Processes for Making Cyclohexanone

ABSTRACT

Disclosed are processes for abating 3-cyclohexenone from a feed mixture comprising cyclohexylbenzene, cyclohexanone, phenol, and 3-cylclohexenone and cyclohexanone, comprising feeding the feed mixture to a first distillation column and a hydrogenating a fraction from in the presence of a hydrogenation catalyst under hydrogenation conditions. Hydrogenation can be carried out in a hydrogenation reactor separate from the first distillation column or in a hydrogenation zone disposed inside the first distillation column.

PRIORITY

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 62/525,922, filed Jun. 28, 2017, which is incorporatedherein by reference.

FIELD

The present invention relates to processes for making cyclohexanone. Inparticular, the present invention relates to processes for makingcyclohexanone including a step of abating 3-cyclohexenone from a processstream. The present invention is useful, e.g., in making tocyclohexanone from cyclohexylbenzene oxidation and cyclohexylbenzenehydroperoxide cleavage.

BACKGROUND

Cyclohexanone is an important material in the chemical industry and iswidely used in, for example, production of phenolic resins, bisphenol A,caprolactam, adipic acid, and plasticizers. One method for makingcyclohexanone is by hydrogenating phenol.

Currently, a common route for the production of phenol is the Hockprocess. This is a three-step process in which the first step involvesalkylation of benzene with propylene to produce cumene, followed byoxidation of cumene to the corresponding hydroperoxide, and thencleavage of the hydroperoxide to produce equimolar amounts of phenol andacetone. The separated phenol product can then be converted tocyclohexanone by a step of hydrogenation.

It is known from, e.g., U.S. Pat. No. 6,037,513, that cyclohexylbenzenecan be produced by contacting benzene with hydrogen in the presence of abifunctional catalyst comprising a molecular sieve of the MCM-22 typeand at least one hydrogenation metal selected from palladium, ruthenium,nickel, cobalt, and mixtures thereof. This reference also discloses thatthe resultant cyclohexylbenzene can be oxidized to the correspondinghydroperoxide, which can then be cleaved to produce a cleavage mixtureof phenol and cyclohexanone, which, in turn, can be separated to obtainpure, substantially equimolar phenol and cyclohexanone products. Thiscyclohexylbenzene-based process for co-producing phenol andcyclohexanone can be highly efficient in making these two importantindustrial materials. Given the higher commercial value of cyclohexanonethan phenol, it is highly desirable that in this process morecyclohexanone than phenol be produced. While this can be achieved bysubsequently hydrogenating the pure phenol product produced in thisprocess to convert a part or all of the phenol to cyclohexanone, a moreeconomical process and system would be highly desirable.

One solution to making more cyclohexanone than phenol from the abovecyclohexylbenzene-based process is to hydrogenate a mixture containingphenol and cyclohexanone obtained from the cleavage mixture to convertat least a portion of the phenol contained therein to cyclohexanone.However, because the phenol/cyclohexanone mixture invariably containsnon-negligible amounts of (i) catalyst poison component(s) (such as5-containing components) that can poison the hydrogenation catalyst, and(ii) cyclohexylbenzene that can be converted into bicyclohexane in thehydrogenation step, and because hydrogenation of thephenol/cyclohexanone/cyclohexylbenzene mixture can also lead to theformation of cyclohexanol, resulting in yield loss, this process is notwithout challenge. In short, the unconventional feed to a phenolhydrogenation process, produced by the aforementioned route includinghydroalkylation of benzene, presents a great deal of challenges tomaintaining the desired activity of phenol hydrogenation catalyst, andthe desired selectivity to cyclohexanone.

Recently, the present inventors have found that, in the processincluding cyclohexylbenzene oxidation followed by acid cleavage of thecyclohexylbenzene hydroperoxide process for making cyclohexanone(hereinafter called the “CHB-route”), 2-cyclohexenone and3-cyclohexenone are produced due to various side reactions that mayoccur in the various reactors, especially the cleavage reactor, and oneor both of them can be present as impurities in thecyclohexanone-containing products. The presence of 2-cyclohexenone and3-cyclohexenone impurities at elevated concentrations can cause variousissues in downstream use of the cyclohexanone-containing products, suchas the manufacture of caprolactam. Therefore, there is a need to abatethe concentration of both 2-cyclohexenone and 3-cyclohexenone from thecyclohexanone product.

Some references of potential interest in this regard may include: U.S.Pat. Nos. 3,076,810; 3,322,651; 3,998,884; 4,021,490; 4,200,553;4,203,923; 4,439,409; 4,826,667; 4,954,325; 5,064,507; 5,168,983;5,236,575; 5,250,277; 5,362,697; 6,015,927; 6,037,513; 6,046,365;6,077,498; 6,215,028; 6,730,625; 6,756,030; 7,199,271; 7,579,506;7,579,511; 8,222,459; 8,389,773; 8,618,334; 8,772,550; 8,802,897; and8,921,603. Other references of potential interest include WIPOPublication Nos. WO 97/17290; WO 2009/128984; WO 2009/131769; WO2009/134514; WO 2010/098916; WO 2012/036820; WO 2012/036822; WO2012/036823; WO 2012/036828; WO 2012/036830; WO 2014/137624; andWO2017/023430. Further references of potential interest include EP 0 293032; EP 0 606 553; EP 1 575 892; JP 434156 B2; as well as Alexandre C.Dimian and Costin Sorin Bildea, Chemical Process Design: Computer-AidedCase Studies, pp. 129-172 (Wiley, 2008); Van Peppen, J. F. et al.,Phenol Hydrogenation Process, in Catalysis of Organic Reactions, pp.355-372 (1985, ed. R. L. Augustine); Diaz et al., Hydrogenation ofphenol in aqueous phase with palladium on activated carbon catalysts,CHEM. ENG'G J. 131 (2007) at 65-71; and Gonzalez-Velazco et al.,Activity and selectivity of palladium catalysts during the liquid-phasehydrogenation of phenol: Influence of temperature and pressure,INDUSTRIAL & ENG'G CHEM. RESEARCH (April 1995), Vol. 34, No. 4, p. 1031.

SUMMARY

It has been found that, by subjecting process streams containingcyclohexanone and 3-cyclohexenone and optionally 2-cyclohexenone througha hydrogenation step, such as hydrogenation process designed forhydrogenating phenol, one can successfully hydrogenate 2-cyclohexenoneand 3-cyclohexenone at a high level of conversion, effectively abatingthe concentrations of 2-cyclohexenone and 3-cyclohexenone in the processstream to a low level. From the abated process stream, one can obtain acyclohexanone-containing product depleted of both 2-cyclohexenone and3-cyclohexenone.

Thus, a first aspect of the present disclosure relates to a process forproducing cyclohexanone from a first feed mixture comprisingcyclohexylbenzene, cyclohexanone, phenol, and 3-cyclohexenone, theprocess comprising: feeding the first feed mixture into a firstdistillation column at a first feeding location on the firstdistillation column; obtaining a cyclohexylbenzene-rich lower effluentfrom the first distillation column; obtaining a first upper effluentfrom a first upper effluent location on the first distillation columnabove the first feeding location, the first upper effluent comprisingphenol, cyclohexanone, and 3-cyclohexenone; feeding at least a portionof the first upper effluent to a hydrogenation reactor, where the firstupper effluent contacts with hydrogen in the presence of a hydrogenationcatalyst under hydrogenation conditions to produce a hydrogenationreactor effluent substantially free of 3-cylcohexenone; feeding at leasta portion of the hydrogenation reactor effluent to a second distillationcolumn, and obtaining an cyclohexanone-rich upper effluent and aphenol-rich lower effluent from the second distillation column.

A second aspect of the present disclosure relates to a process forproducing cyclohexanone from a first feed mixture comprisingcyclohexylbenzene, cyclohexanone, phenol, and 3-cyclohexenone, theprocess comprising: feeding the first feed mixture into a firstdistillation column at a first feeding location; providing a reactivehydrogenation zone loaded with a hydrogenation catalyst in the firstdistillation column above the first feeding location; supplying hydrogeninto the first distillation column at a location lower than thehydrogenation zone; converting at least a portion of the 3-cyclohexenonein the hydrogenation zone under hydrogenation conditions; obtaining acyclohexylbenzene-rich lower effluent from the first distillationcolumn; and obtaining a first upper effluent from a first upper effluentlocation on the first distillation column above the reactivehydrogenation zone, the first upper effluent comprising cyclohexanoneand is substantially free of 3-cyclohexenone and phenol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the concentrations of2-cyclohexenone, 3-cyclohexenone, and cyclohexanol of various fractionsobtained from spinning band distillation (“SBD”) of a feed mixtureconsisting of 2-cyclohexenone, 3-cyclohexenone, cyclohexanol, andcyclohexanone.

FIG. 2 is a schematic diagram showing a comparative process/systemincluding a primary fractionator, a phenol hydrogenation reactor, andadditional distillation columns, resulting in high concentration of3-cyclohexenone in the cyclohexanone product.

FIG. 3 is a schematic diagram showing an inventive process/systemincluding a primary fractionator, a phenol hydrogenation reactor, andadditional distillation columns, resulting in low concentration of3-cyclohexenone in the cyclohexanone product.

FIG. 4 is a schematic diagram showing another inventive process/systemincluding a reactive distillation column performing both the functionsof a hydrogenation reactor and a primary fractionator, and additionaldistillation columns, resulting in low concentration of 3-cyclohexenonein the cyclohexanone product.

FIG. 5 is a schematic diagram showing yet another inventiveprocess/system including a primary fractionator, a hydrogenationreactor, and additional distillation columns, with specializedconfiguration resulting in low concentration of 3-cyclohexenone in thecyclohexanone product.

DETAILED DESCRIPTION

In the present disclosure, a process is described as comprising at leastone “step.” It should be understood that each step is an action oroperation that may be carried out once or multiple times in the process,in a continuous or discontinuous fashion. Unless specified to thecontrary or the context clearly indicates otherwise, steps in a processmay be conducted sequentially in the order as they are listed, with orwithout overlapping with one or more other step, or in any other order,as the case may be. In addition, one or more or even all steps may beconducted simultaneously with regard to the same or different batch ofmaterial. For example, in a continuous process, while a first step in aprocess is being conducted with respect to a raw material just fed intothe beginning of the process, a second step may be carried outsimultaneously with respect to an intermediate material resulting fromtreating the raw materials fed into the process at an earlier time inthe first step. Preferably, the steps are conducted in the orderdescribed.

Unless otherwise indicated, all numbers indicating quantities in thepresent disclosure are to be understood as being modified by the term“about” in all instances. It should also be understood that the precisenumerical values used in the specification and claims constitutespecific embodiments. Efforts have been made to ensure the accuracy ofthe data in the examples. However, it should be understood that anymeasured data inherently contain a certain level of error due to thelimitation of the technique and equipment used for making themeasurement.

I. Definitions

As used herein, the indefinite article “a” or “an” shall mean “at leastone” unless specified to the contrary or the context clearly indicatesotherwise. Thus, embodiments comprising “a light component” includeembodiments where one, two or more light components exist, unlessspecified to the contrary or the context clearly indicates that only onelight component exists.

A “complex” as used herein means a material formed by identifiedcomponents via chemical bonds, hydrogen bonds, and/or physical forces.

An “operation temperature” of a distillation column means the highesttemperature liquid media inside the column is exposed to during normaloperation. Thus, the operation temperature of a column is typically thetemperature of the liquid media in the reboiler, if the column isequipped with a reboiler.

The term “S-containing component” as used herein includes all compoundscomprising sulfur.

In the present application, sulfur concentration in a material isexpressed in terms of proportion (ppm, weight percentages, and the like)of the weight of elemental sulfur relative to the total weight of thematerial, even though the sulfur may be present in various valenciesother than zero. Sulfuric acid concentration is expressed in terms ofproportion (ppm, weight percentages, and the like) of the weight ofH₂SO₄ relative to the total weight of the material, even though thesulfuric acid may be present in the material in forms other than H₂SO₄.Thus, the sulfuric acid concentration is the total concentration ofH₂SO₄, SO₃, HSO₄—, and R—HSO₄ in the material.

As used herein, “wt %” means percentage by weight, “vol %” meanspercentage by volume, “mol %” means percentage by mole, “ppm” meansparts per million, and “ppm wt” and “ppm by weight” are usedinterchangeably to mean parts per million on a weight basis. All “ppm”as used herein are ppm by weight unless specified otherwise. Allconcentrations herein are expressed on the basis of the total amount ofthe composition in question, unless otherwise noted. Thus, absent acontrary indication, the concentrations of the various components of afirst mixture are expressed based on the total weight of the firstmixture. All ranges expressed herein should include both end points astwo specific embodiments unless specified or indicated to the contrary.

In the present disclosure, a location “in the vicinity of” an end (topor bottom) of a column means a location within 10% of the top or bottom,respectively, the % being based upon the total height of the column.That is, a location “in the vicinity of the bottom” of a column iswithin the bottom 10% of the column's height, and a location “in thevicinity of the top” of a column is within the top 10% of the column'sheight.

An “upper effluent” as used herein may be at the very top or the side ofa vessel such as a distillation column or a reactor, with or without anadditional effluent above it. Preferably, an upper effluent is drawn ata location in the vicinity of the top of the column. Preferably, anupper effluent is drawn at a location above at least one feed. A “lowereffluent” as used herein is at a location lower than the upper effluent,which may be at the very bottom or the side of a vessel, and if at theside, with or without additional effluent below it. Preferably, a lowereffluent is drawn at a location in the vicinity of the bottom of thecolumn. Preferably, a lower effluent is drawn at a location below atleast one feed. As used herein, a “middle effluent” is an effluentbetween an upper effluent and a lower effluent. The “same level” on adistillation column means a continuous segment of the column with atotal height no more than 5% of the total height of the column. In thepresent disclosure, the term “fraction” and “effluent” are usedinterchangeably.

Nomenclature of elements and groups thereof used herein are pursuant tothe Periodic Table used by the International Union of Pure and AppliedChemistry after 1988. An example of the Periodic Table is shown in theinner page of the front cover of Advanced Inorganic Chemistry, 6^(th)Edition, by F. Albert Cotton et al. (John Wiley & Sons, Inc., 1999).

As used herein, the term “methylcyclopentanone” includes both isomers2-methylcyclopentanone (CAS Registry No. 1120-72-5) and3-methylcyclopentanone (CAS Registry No. 1757-42-2), at any proportionbetween them, unless it is clearly specified to mean only one of thesetwo isomers or the context clearly indicates that is the case. It shouldbe noted that under the conditions of the various steps of the presentprocesses, the two isomers may undergo isomerization reactions to resultin a ratio between them different from that in the raw materialsimmediately before being charged into a vessel such as a distillationcolumn.

As used herein, the generic term “dicyclohexylbenzene”(“Dicyclohexylbenzene”) includes, in the aggregate,1,2-dicyclohexylbenzene, 1,3-dicylohexylbenzene, and1,4-dicyclohexylbenzene, unless clearly specified to mean only one ortwo thereof. The term cyclohexylbenzene, when used in the singular form,means mono substituted cyclohexylbenzene. As used herein, the term “C12”means compounds having 12 carbon atoms, and “C12+ components” meanscompounds having at least 12 carbon atoms. Examples of C12+ componentsinclude, among others, cyclohexylbenzene, biphenyl, bicyclohexane,methylcyclopentylbenzene, 1,2-biphenylbenzene, 1,3-biphenylbenzene,1,4-biphenylbenzene, 1,2,3-triphenylbenzene, 1,2,4-triphenylbenzene,1,3,5-triphenylbenzene, and corresponding to oxygenates such asalcohols, ketones, acids, and esters derived from these compounds. Asused herein, the term “C18” means compounds having 18 carbon atoms, andthe term “C18+ components” means compounds having at least 18 carbonatoms. Examples of C18+ components include, among others,dicyclohexylbenzenes (“Dicyclohexylbenzene,” described above),tricyclohexylbenzenes (“Tricyclohexylbenzene,” including all isomersthereof, including 1,2,3-tricyclohexylbenzene,1,2,4-tricyclohexylbenzene, 1,3,5-tricyclohexylbenzene, and mixtures oftwo or more thereof at any proportion). As used herein, the term “C24”means compounds having 24 carbon atoms.

In the present disclosure, when the word “rich” is used in describing acomponent in a given effluent or a mixture produced from a vessel,reactor or distillation column, it means the concentration of thecomponent in that given effluent or mixture is higher than itsconcentration in a feed supplied into the vessel, reactor ordistillation column.

In the present disclosure, when the word “depleted” is used indescribing a component in a given effluent or a mixture produced from avessel, reactor or distillation column, it means the concentration ofthe component in that given effluent or mixture is lower than itsconcentration in a feed supplied into the vessel, reactor ordistillation column.

In the present disclosure, the term “light components” means componentshaving a normal boiling point lower than cyclohexanone.

In the present disclosure, the term “light acid” means acid having anormal boiling point lower than cyclohexanone.

In the present disclosure, the term “substantially free of phenol” meanscomprising phenol at a concentration no higher than 100 (preferably nohigher than 50, still more preferably no higher than 20, still morepreferably no higher than 10) ppm by weight, based on the total weightof the material in question.

As used herein, the term “2-cyclohexenone” means a compound having theformula:

2-cyclohexenone can be separated from cyclohexanone by conventionaldistillation, as demonstrated in Example 1 herein. 2-cyclohexenone, ifincluded in a cyclohexanone product at elevated concentrations, cancause problems in downstream use of the product, e.g., in makingcaprolactam used for making nylon-6, a commercially important polyamide.Thus, it is highly desirable that a cyclohexanone product contain2-cyclohexenone at a low concentration, e.g., no higher than 100, 80,60, 50, 40, 30, 20, or 10, ppm by weight, based on the total weight ofthe product. For the purpose of the present disclosure, a composition ofmatter comprising 2-cyclohexenone at a concentration no higher than 20ppm is considered as “substantially free” of 2-cyclohexenone.

As used herein, the term “3-cyclohexenone” means a compound having theformula:

To the surprise of the inventors, 3-cyclohexenone, although a structuralisomer of 2-cyclohexenone, cannot be completely separated fromcyclohexanone by conventional distillation, as demonstrated in Example 1herein. Likewise, 3-cyclohexenone, if included in a cyclohexanoneproduct at elevated concentrations, can cause problems in downstream useof the product, e.g., in making caprolactam. Thus, it is highlydesirable that a cyclohexanone product contain 3-cyclohexenone at a lowconcentration, e.g., no higher than 100, 80, 60, 50, 40, 30, 20, or 10,ppm by weight, based on the total weight of the product. Withoutintending to be bound by a particular theory, it is believed that thedifference in behaviors of 2-cyclohexenone and 3-cyclohexenone in theirmixtures with cyclohexanone can be explained by the location of the C═Cbond relative to the C═O bond in the molecules. In 2-cyclohexenone, thetwo double bonds are conjugated, while in 3-cyclohexenone, they are not,leading to significantly different affinity to cyclohexanone. For thepurpose of the present disclosure, a composition of matter comprising3-cyclohexenone at a concentration no higher than 20 ppm is consideredas “substantially free” of 3-cyclohexenone.

II. General Description of Hydrogenation of Feed Mixture ComprisingCyclohexanone and 3-Cyclohexenone

Since simple conventional distillation cannot be used to completelyseparate 3-cyclohexenone from cyclohexanone, the present inventorscontemplated specialized distillation approaches and chemical approachesto abate the 3-cyclohexenone concentration in a cyclohexanone-containingfeed mixture. An exemplary specialized distillation process isillustrated in Example 5 herein. One particularly effective chemicalapproach is hydrogenation of the 3-cyclohexenone andcyclohexanone-containing feed mixture: contacting the feed mixture withhydrogen in the presence of a hydrogenation catalyst under hydrogenationconditions. The C═C bond in the 3-cyclohexenone molecule can beconveniently saturated to produce cyclohexanone, thereby converting3-cyclohexenone as a contaminant into the desirable product. If the feedmixture also contains 2-cyclohexenone, which can be the case if the feedmixture is prepared via the CHB-route for making cyclohexanone and/orphenol as described in detail below, the 2-cyclohexenone can beconverted into cyclohexanone as well. Hydrogenation conditions can bechosen such that the conversion of 3-cyclohexenone and/or2-cyclohexenone can be up to 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, oreven 99.9%, or even higher, resulting in a hydrogenated mixture depletedof 2-cyclohexenone and 3-cyclohexenone, comprising each at aconcentration no higher than 100, 80, 60, 50, 40, 30, 20, 10, 8, 6, 5,4, 2, 1, 0.8, 0.6, 0.5, 0.4, 0.2, 0.1, 0.08, 0.06, 0.05, 0.04, 0.02, oreven 0.01 ppm by weight based on the total weight of the hydrogenatedmixture. It is also possible to achieve a total concentration of2-cyclohexenone and 3-cyclohexenone combined of no higher than 100, 80,60, 50, 40, 30, 20, 10, 8, 6, 5, 4, 2, 1, 0.8, 0.6, 0.5, 0.4, 0.2, 0.1,0.08, 0.06, 0.05, 0.04, 0.02, or even 0.01 ppm by weight based on thetotal weight of the hydrogenated mixture. The hydrogenated mixture, ifcomprising substantially only cyclohexanone and preferably substantiallyfree of 2-cyclohexenone and 3-cyclohexenone, can then be used as iswithout the issues caused by 2-cyclohexenone and 3-cyclohexenone; and ifcomprising cyclohexanone at a relatively low concentration, can then beseparated by conventional distillation to make a high-puritycyclohexanone product depleted of 2-cyclohexenone and 3-cyclohexenone,preferably substantially free of 2-cyclohexenone and 3-cyclohexenone.

Desirably, the feed mixture fed into the hydrogenation step comprisesone or both of the 2-cyclohexenone and 3-cyclohexenone each at arelatively low concentration, each independently from a1 to a2 ppm byweight, based on the total weight of the feed mixture, where a1 and a2can be, independently, 10, 20, 30, 40, 50, 80, 100, 200, 400, 500, 600,800, 1000, 2000, 4000, 5000, 6000, 8000, 1×10⁴, 2×10⁴, 4×10⁴, 5×10⁴,6×10⁴, 8×10⁴, 1×10⁵, 2×10⁵, 4×10⁵, 5×10⁵, 6×10⁵, 8×10⁵, 1×10⁶, 2×10⁶,4×10⁶, 5×10⁶, as long as a1<a2. Preferably a1=50, a2=2000. Morepreferably a1=100, a2=1000.

The feed mixture undergoing the hydrogenation step may comprisecyclohexanone at a concentration in the range from b1 to b2 wt %, basedon the total weight of the feed mixture, where b1 and b2 can be,independently, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98,or 99, as long as b1<b2. Some of the cyclohexanone may also undergohydrogenation in the process to produce cyclohexanol. The quantity ofcyclohexanol produced in the hydrogenation step can be controlled byselecting the catalyst and hydrogenation conditions such as temperature,residence time, and hydrogen partial pressure, depending on the exactmake-up of the feed mixture. Cyclohexanol can form a mixture withcyclohexanone to obtain KA oil, a saleable product useful for makingadipic acid, which, in turn, can be used for making nylon-6,6, anothercommercially significant polyamide.

The feed mixture undergoing the hydrogenation step can advantageouslycomprise phenol at a concentration in the range from c1 to c2 wt %,based on the total weight of the feed mixture, where c1 and c2 can be,independently, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, or98, as long as c1<c2. Desirably, in the hydrogenation step, at least aportion of the phenol included in the feed mixture is also hydrogenatedto form cyclohexanone. Desirably, the conversion of phenol in thehydrogenation step is in a range from d1% to d2%, where d1 and d2 canbe, independently, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92,93, 94, 95, 96, 97, 98, or 99, as long as d1<d2. Thus, in thehydrogenation step, phenol, 2-cyclohexenone, and 3-cyclohexenone can allbe advantageously converted to cyclohexanone, the desired product.

It has been found that, surprisingly, in a hydrogenation reactor loadedwith a hydrogenation catalyst and operating under hydrogenationconditions conducive to converting at least a portion of phenol tocyclohexanone, the reaction rates of 2-cyclohexenone hydrogenation and3-cyclohexenone hydrogenation to form cyclohexanone are much faster thanthe reaction of phenol hydrogenation to form cyclohexanone. As such, aslong as phenol is converted into cyclohexanone at a significantconversion (e.g., at least 20, 30, 40, 50, or 60 percent), theconversion of 2-cyclohexenone and 3-cyclohexenone tend to be muchhigher, reaching at least 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.9,or even 99.99 percent, or even higher, resulting in substantially totaldepletion of 2-cyclohexenone and 3-cyclohexenone in the hydrogenatedmixture at the exceedingly low concentrations as described above.

The feed mixture may also comprise cyclohexanol at a concentration inthe range from d1 to d2 wt %, based on the total weight of the feedmixture, where d1 and d2 can be, independently, 0.1, 0.5, 1, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, as long as d1<d2.

An exemplary feed mixture that can be produced from the CHB-routedescribed in detail below can comprise cyclohexanone at a concentrationin the range from 1 to 50 wt % (preferably 2 to 40 wt %, more preferably3 to 30 wt %, still more preferably 5 to 25 wt %), phenol at aconcentration from 1 to 90 wt % (preferably 10 to 90 wt %, morepreferably 20 to 90 wt %, still more preferably 30 to 90 wt %, stillmore preferably 40 to 90 wt %, still more preferably 50 to 90 wt %),cyclohexanol from 0 to 50 wt % (preferably 0 to 40 wt %, more preferably0 to 30 wt %, still more preferably 0 to 20 wt %, still more preferably0 to 10 wt %, still more preferably 0 to 5 wt %), 3-cyclohexenone at aconcentration in the range from 30 to 2000 ppm (preferably 50 to 1000ppm), and optionally 2-cyclohexenone at a concentration in the rangefrom 30 to 2000 ppm (preferably 50 to 1000 ppm), based on the totalweight of the feed mixture. The hydrogenated mixture resulting from thisfeed mixture can comprise cyclohexanone at a concentration in the rangefrom 5 to 99.99 wt %, 3-cyclohexenone at a concentration in the rangefrom 0.01 to 20 ppm (preferably from 0.01 to 10 ppm), and2-cyclohexenone at a concentration in the range from 0.01 to 20 ppm(preferably from 0.01 to 10 ppm), based on the total weight of thehydrogenated mixture.

Hydrogenation catalyst suitable for the hydrogenation step typicallycomprises a hydrogenation metal such as Fe, Co, Ni, Ru, Rh, Pd, Ag, Re,Os, Ir, and Pt, and mixtures and combinations of one or more thereof. Pdis a particularly preferred hydrogenation metal according to anyembodiment. Additional details of the hydrogenation catalyst are givenlater in the present disclosure. The hydrogenation conditions can bechosen such that (i) at least 80% of cyclohexanone is present in liquidphase (“liquid-phase hydrogenation”), or at least 80% of cyclohexanoneis present in vapor phase (“vapor-phase hydrogenation”), or more than20% and less than 80% of cyclohexanone is present in liquid phase(“mixed-phase hydrogenation”). In general, the reaction temperature isin the range from 25 to 300° C. (e.g., from 40 to 250, or from 50 to200° C.), and the absolute hydrogen partial pressure can be in the rangefrom 50 to 2000 kPa (e.g., from 60 to 1000 kPa, or from 80 to 800 kPa,or from 90 to 600 kPa, or from 100 to 500 kPa).

The general approach of subjecting the feed mixture to a hydrogenationstep can be used to abate 3-cyclohexenone and/or 2-cyclohexenonecontained in any cyclohexanone-containing materials, irrespective of thespecific method of making.

III. The CHB-Route for Making Cyclohexanone and/or Phenol

The CHB-route for making cyclohexanone and/or phenol starts with a stepof making cyclohexylbenzene from benzene and hydrogen in the presence ofa hydroalkylation catalyst. The cyclohexylbenzene thus produced is thenoxidized to form its hydroperoxide, which is then subject to a cleavagereaction in the presence of an acid catalyst to obtain cyclohexanone andphenol. Various separation and purification process can be carried outsubsequently to obtain high-purity cyclohexanone and phenol as products,or at least a portion of the phenol can be hydrogenated to makeadditional cyclohexanone and optionally cyclohexanol. The CHB-route canproduce multiple feed mixture containing both cyclohexanone and3-cyclohexenone and optionally 2-cyclohexenone at variousconcentrations. The process and system of the present disclosure can beadvantageously used to abate the concentration of 3-cyclohexenone and2-cyclohexenone in those feed mixtures. Detailed description of theprocess steps of the CHB-route follows.

III.1 Supply of Cyclohexylbenzene

The cyclohexylbenzene supplied to the oxidation step can be producedand/or recycled as part of an integrated process for producing phenoland cyclohexanone from benzene. In such an integrated process, benzeneis initially converted to cyclohexylbenzene by any conventionaltechnique, including oxidative coupling of benzene to make biphenylfollowed by hydrogenation of the biphenyl. However, in practice, thecyclohexylbenzene is desirably produced by contacting benzene withhydrogen under hydroalkylation conditions in the presence of ahydroalkylation catalyst whereby benzene undergoes the followingReaction-1 to produce cyclohexylbenzene:

Alternatively, cyclohexylbenzene can be produced by direct alkylation ofbenzene with cyclohexene in the presence of a solid-acid catalyst suchas molecular sieves in the MCM-22 family according to the followingReaction-2:

Side reactions may occur in Reaction-1 or Reaction-2 to produce somepolyalkylated benzenes, such as dicyclohexylbenzenes(Dicyclohexylbenzene), tricyclohexylbenzenes (Tricyclohexylbenzene),methylcyclopentylbenzene, unreacted benzene, cyclohexane, bicyclohexane,biphenyl, and other contaminants. Thus, typically, after the reaction,the hydroalkylation reaction product mixture is separated bydistillation to obtain a C6 fraction containing benzene, cyclohexane, aC12 fraction containing cyclohexylbenzene and methylcyclopentylbenzene,and a heavies fraction containing, e.g., C18s such asDicyclohexylbenzenes and C24s such as Tricyclohexylbenzenes. Theunreacted benzene may be recovered by distillation and recycled to thehydroalkylation or alkylation reactor. The cyclohexane may be sent to adehydrogenation reactor, with or without some of the residual benzene,and with or without co-fed hydrogen, where it is converted to benzeneand hydrogen, which can be recycled to the hydroalkylation/alkylationstep. Depending on the quantity of the heavies fraction, it may bedesirable to either (a) transalkylate the C18s such asDicyclohexylbenzene and C24s such as Tricyclohexylbenzene withadditional benzene or (b) dealkylate the C18s and C24s to maximize theproduction of the desired monoalkylated species.

Details of feed materials, catalyst used, reaction conditions, andreaction product properties of benzene hydroalkylation, andtransalkylation and dealkylation can be found in, e.g., the followingcopending, co-assigned patent applications: U.S. Provisional PatentApplication Ser. Nos. 61/972,877, entitled “Process for MakingCyclohexylbenzene and/or Phenol and/or Cyclohexanone;” and filed on Mar.31, 2014; U.S. Provisional Patent Application Ser. No. 62/037,794,entitled “Process and System for Making Cyclohexanone,” and filed onAug. 15, 2014; U.S. Provisional Patent Application Ser. No. 62/037,801,entitled “Process and System for Making Cyclohexanone,” and filed onAug. 15, 2014; U.S. Provisional Patent Application Ser. No. 62/037,814,entitled “Process and System for Making Cyclohexanone,” and filed onAug. 15, 2014; U.S. Provisional Patent Application Ser. No. 62/037,824,entitled “Process and System for Making Cyclohexanone,” and filed onAug. 15, 2014; U.S. Provisional Patent Application Ser. No. 62/057,919,entitled “Process for Making Cyclohexanone,” and filed on Sep. 30, 2014;U.S. Provisional Patent Application Ser. No. 62/057,947, entitled“Process for Making Cyclohexanone,” and filed on Sep. 30, 2014; and U.S.Provisional Patent Application Ser. No. 62/057,980, entitled “Processfor Making Cyclohexanone,” and filed on Sep. 30, 2014, the contents ofall of which are incorporated herein by reference in their entirety.

III.2 Oxidation of Cyclohexylbenzene

In the oxidation step, at least a portion of the cyclohexylbenzenecontained in the oxidation feed is converted tocyclohexyl-1-phenyl-1-hydroperoxide, the desired hydroperoxide,according to the following Reaction-3:

The cyclohexylbenzene freshly produced and/or recycled may be purifiedbefore being fed to the oxidation step to remove at least a portion of,among others, methylcyclopentylbenzene, olefins, phenol, acid, and thelike. Such purification may include, e.g., distillation, hydrogenation,caustic wash, and the like.

In exemplary processes, the oxidation step may be accomplished bycontacting an oxygen-containing gas, such as air and various derivativesof air, with the feed comprising cyclohexylbenzene. For example, astream of pure O₂, O₂ diluted by inert gas such as N₂, pure air, orother O₂-containing mixtures can be pumped through thecyclohexylbenzene-containing to feed in an oxidation reactor to effectthe oxidation.

The oxidation may be conducted in the absence or presence of a catalyst,such as a cyclic imide type catalyst (e.g., N-hydroxyphthalimide).

Details of the feed material, reaction conditions, reactors used,catalyst used, product mixture composition and treatment, and the like,of the oxidation step can be found in, e.g., the following copending,co-assigned patent applications: U.S. Provisional Patent ApplicationSer. Nos. 61/972,877, entitled “Process for Making Cyclohexylbenzeneand/or Phenol and/or Cyclohexanone;” and filed on Mar. 31, 2014; U.S.Provisional Patent Application Ser. No. 62/037,794, entitled “Processand System for Making Cyclohexanone,” and filed on Aug. 15, 2014; U.S.Provisional Patent Application Ser. No. 62/037,801, entitled “Processand System for Making Cyclohexanone,” and filed on Aug. 15, 2014; U.S.Provisional Patent Application Ser. No. 62/037,814, entitled “Processand System for Making Cyclohexanone,” and filed on Aug. 15, 2014; U.S.Provisional Patent Application Ser. No. 62/037,824, entitled “Processand System for Making Cyclohexanone,” and filed on Aug. 15, 2014; U.S.Provisional Patent Application Ser. No. 62/057,919, entitled “Processfor Making Cyclohexanone,” and filed on Sep. 30, 2014; U.S. ProvisionalPatent Application Ser. No. 62/057,947, entitled “Process for MakingCyclohexanone,” and filed on Sep. 30, 2014; and U.S. Provisional PatentApplication Ser. No. 62/057,980, entitled “Process for MakingCyclohexanone,” and filed on Sep. 30, 2014, the contents of all of whichare incorporated herein by reference in their entirety.

III.3 Cleavage Reaction

In the cleavage reaction, at least a portion of thecyclohexyl-1-phenyl-1-hydroperoxide decomposes in the presence of anacid catalyst in high selectivity to cyclohexanone and phenol accordingto the following desired Reaction-4:

The cleavage product mixture may comprise the acid catalyst, phenol,cyclohexanone, cyclohexylbenzene, and contaminants such as3-cyclohexenone and optionally 2-cyclohexenone.

The acid catalyst can be at least partially soluble in the cleavagereaction mixture, is stable at a temperature of at least 185° C. and hasa lower volatility (higher normal boiling point) than cyclohexylbenzene.

Feed composition, reaction conditions, catalyst used, product mixturecomposition and treatment thereof, and the like, of this cleavage stepcan be found in, e.g., the following copending, co-assigned patentapplications: U.S. Provisional Patent Application Ser. Nos. 61/972,877,entitled “Process for Making Cyclohexylbenzene and/or Phenol and/orCyclohexanone;” and filed on Mar. 31, 2014; U.S. Provisional PatentApplication Ser. No. 62/037,794, entitled “Process and System for MakingCyclohexanone,” and filed on Aug. 15, 2014; U.S. Provisional PatentApplication Ser. No. 62/037,801, entitled “Process and System for MakingCyclohexanone,” and filed on Aug. 15, 2014; U.S. Provisional PatentApplication Ser. No. 62/037,814, entitled “Process and System for MakingCyclohexanone,” and filed on Aug. 15, 2014; U.S. Provisional PatentApplication Ser. No. 62/037,824, entitled “Process and System for MakingCyclohexanone,” and filed on Aug. 15, 2014; U.S. Provisional PatentApplication Ser. No. 62/057,919, entitled “Process for MakingCyclohexanone,” and filed on Sep. 30, 2014; U.S. Provisional PatentApplication Ser. No. 62/057,947, entitled “Process for MakingCyclohexanone,” and filed on Sep. 30, 2014; and U.S. Provisional PatentApplication Ser. No. 62/057,980, entitled “Process for MakingCyclohexanone,” and filed on Sep. 30, 2014, the contents of all of whichare incorporated herein by reference in their entirety.

III.4 Post-Cleavage Treatment

The cleavage mixture exiting the cleavage reactor comprise, in additionto phenol, cyclohexanone, cyclohexylbenzene, acid catalyst if a liquidacid such as sulfuric acid is used in the cleavage step, and othercontaminants Before the cleavage mixture is supplied to a firstdistillation column to separate the various components, the acid isremoved or neutralized to prevent undesirable side reactions catalyzedby the acid in the first distillation column.

Preferably, a solid state basic material is used to neutralize the acidin the cleavage mixture. Doing so would reduce or eliminate the presenceof acid species and/or S-containing components in media inside the firstdistillation column, avoid undesirable side reactions and byproductsformed as a result of contact with the acid species, reduce corrosion ofthe first distillation column caused by the acid species and theassociated repair and premature replacement, and prevent undesirableside reactions and byproduct formation in subsequent steps.

Such basic materials useful for treatment according to such embodiments,advantageously in solid-phase under the operation conditions, can beselected from (i) oxides of alkali metals (e.g., Na), alkaline earthmetals (e.g., Mg), and zinc; (ii) hydroxides of alkali metals (e.g.,Na), alkaline earth metals (e.g., Mg), and zinc; (iii) carbonates ofalkali metals (e.g., Na), alkaline earth metals (e.g., Mg), and zinc;(iv) bicarbonates of alkali metals (e.g., Na), alkaline earth metals(e.g., Mg), and zinc; (v) complexes of two or more of (i), (ii), (iii),and (iv); (vi) solid amines; (vii) ion-exchange resins; and (viii)mixtures and combinations of two or more of (i), (ii), (iii), (iv), (v),(vi), and (vii). Oxides, hydroxides, carbonates and bicarbonates ofalkali and alkaline earth metals and zinc can react with acid to formsalts thereof, which preferably, are also in solid-phase under theoperation conditions. Preferably, an ion exchange resin is used. Suchion exchange resins preferably comprise groups on the surface thereofcapable of adsorbing and/or binding with protons, SO₃, HSO₄—, H₂SO₄,complexes of sulfuric acid, and the like. The ion exchange resin cancomprise a strong and/or a weak base resin. Weak base resins primarilyfunction as acid adsorbers. These resins are capable of adsorbing strongacids with a high capacity. Strong base anion resins can comprisequarternized amine-based products capable of adsorbing both strong andweak acids. Commercial examples of basic ion exchange resins useful inthe present invention include but are not limited to: Amberlyst® A21 andAmberlyst® A26 basic ion exchange resins available from Dow ChemicalCompany. Amberlyst® A26 is an example of a strong base, type 1, anionic,macroreticular polymeric resin. According to Dow Chemical Company, theresin is based on crosslinked styrene divinylbenzene copolymer,containing quaternary ammonium groups. A26 is generally considered to bea stronger base resin than A21.

After treatment using a solid-phase base and/or ion exchange resin, bothtotal acid concentration and acid precursor concentration (includingconcentration of S-containing components) in the feed supplied to thefirst distillation column can be exceedingly low (e.g., 50 ppm or less,such as less than or equal to 20, 15, 10, 5, or 1 ppm). Accordingly, thefirst distillation column can be operated at a high operationtemperature, such as temperatures higher than the disassociationtemperatures of complex materials formed between the acid catalyst usedin the cleavage step, such as sulfuric acid, and the following organicamines: (i) pentane-1,5-diamine; (ii) 1-methylhexane-1,5-diamine; (iii)hexane-1,6-diamine; (iv) 2-methylpentane-1,5-diamine; (v) ethylenediamine; (vi) propylene diamine; (vii) diethylene triamine; and (viii)triethylene tetramine, without the concern of issues associated withacid produced from thermal dissociation thereof under such highoperation temperature.

Additional detailed description of post-cleavage treatment of thecleavage mixture can be found in WO 2017/023430, the relevant portion ofwhich is incorporated herein by reference in its entirety.

III.5 Separation and Purification

The neutralized cleavage reaction product can then be separated bymethods such as distillation. In one example, in a first distillationcolumn after the cleavage reactor, a heavies fraction (a lower effluent)comprising heavies (such as amine sulfuric acid complex, which can beregarded as an amine sulfate salt, if an organic amine is used toneutralize at least a portion of the sulfuric acid present in thecleavage reaction product before it is fed into the first distillationcolumn) is obtained at the bottom of the column, a side fraction(equivalent to a middle effluent) comprising cyclohexylbenzene isobtained in the middle section, and an upper fraction (equivalent to anupper effluent) comprising cyclohexanone, phenol, methylcyclopentanone,3-cyclohexenone and/or 2-cyclohexenone, and water is obtained.

The separated cyclohexylbenzene fraction can then be treated and/orpurified before being delivered to the oxidation step. Since thecyclohexylbenzene separated from the cleavage product mixture maycontain phenol and/or olefins such as cyclohexenylbenzenes, the materialmay be subjected to treatment with an aqueous composition comprising abase and/or a hydrogenation step as disclosed in, for example, WO2011/100013A1, the entire contents of which are incorporated herein byreference.

In one example, the fraction comprising phenol, cyclohexanone,3-cyclohexenone and/or 2-cyclohexenone, and water can be furtherseparated by simple distillation to obtain an upper fraction comprisingprimarily cyclohexanone and methylcyclopentanone and a lower fractioncomprising primarily phenol, and some cyclohexanone. Cyclohexanonecannot be completely separated from phenol without using an extractivesolvent due to an azeotrope formed between these two. Thus, the upperfraction can be further distillated in a separate column to obtain acyclohexanone product in the vicinity of the bottom and an impurityfraction in the vicinity of the top comprising primarilymethylcyclopentanone, which can be further purified, if needed, and thenused as a useful industrial material. Because 3-cyclohexenone cannot becompletely separated from cyclohexanone by conventional distillation,the cyclohexanone product may need to be subject to a hydrogenation stepto abate the 3-cyclohexenone to a desirable level. The lower fractioncan be further separated by a step of extractive distillation using anextractive solvent (e.g., sulfolane, and glycols such as ethyleneglycol, propylene glycol, diethylene glycol, triethylene glycol, and thelike) described in, e.g., co-assigned, co-pending patent applications WO2013/165656A1 and WO 2013/165659, the contents of which are incorporatedherein by reference in their entirety. An upper fraction comprisingcyclohexanone and a lower fraction comprising phenol and the extractivesolvent can be obtained. In a subsequent distillation column, the lowerfraction can then be separated to obtain an upper fraction comprising aphenol product and a lower fraction comprising the extractive solvent.The upper fraction rich in cyclohexanone, if containing 3-cyclohexenone,can be likewise subject to a hydrogenation step to abate the3-cyclohexenone concentration to a desirable level, preferably combinedtogether with other cyclohexanone-rich streams containing3-cyclohexenone in need of abatement.

III.6 Separation and Hydrogenation Reaction

At least a portion, preferably the entirety, of the neutralized cleavageeffluent (cleavage reaction product), may be separated and aphenol-containing fraction thereof can be provided as a feed mixturesupplied to a hydrogenation zone, where at least a portion of the phenolis hydrogenated to form cyclohexanone. The phenol-containing fractioncan contain cyclohexanone, 3-cyclohexenone and optionally2-cyclohexenone. As discussed above, under the typical hydrogenationconditions adapted for phenol hydrogenation, 3-cyclohexenone and2-cyclohexenone tend to convert at a much higher reaction rate thanphenol, and if 3-cyclohexenone and 2-cyclohexenone are incorporated at arelatively low concentration, such as at most 5 wt %, a great majority,and even substantially all of 3-cyclohexenone and 2-cyclohexenone can beconverted to cyclohexanone. Thus, any embodiment of the process mayinclude providing a phenol-containing hydrogenation feed to ahydrogenation reaction zone, wherein the phenol-containing hydrogenationfeed comprises the phenol-containing fraction from the aforementionedseparation of a cleavage effluent. In any embodiment, the hydrogenationfeed may further comprise one or more recycle streams or other streamscomprising a higher weight % of either phenol or cyclohexanone, ascompared to the phenol-containing stream drawn from separation. Thus,the hydrogenation feed may have a weight ratio of phenol tocyclohexanone within the range of 0.15 to 4.0. In any embodiment, theweight ratio is within the range of 0.15 to 0.9 (e.g., where acyclohexanone-containing stream is combined with the hydrogenation feed,and/or wherein the phenol-containing stream withdrawn from separation ofthe cleavage reaction product contains most or all of the cyclohexanonein the cleavage reaction product), whereas in others, it is within therange of 1.0 to 4.0, preferably 2.0 to 4.0.

A hydrogenation reaction zone may comprise any one or more hydrogenationreactors, which reactors may be arranged in series, in parallel, or inany combination thereof. For ease of illustration, many figures andtheir accompanying discussions in the ensuing description include only asingle hydrogenation reactor, but it should be understood that anyembodiment may employ multiple hydrogenation reactors arranged in seriesor in parallel in place of such hydrogenation reactors. Further,multiple hydrogenation reactors (whether in series or in parallel) maybe employed, and/or hydrogen supply may be staged across such multiplereactors, so that each reactor can receive hydrogen feed. A preferredhydrogenation reactor according to any embodiment (any one or more ofwhich may constitute a hydrogenation reaction zone) is a shell-and-tubestype hydrogenation reactor. Such a reactor may comprise one or moretubes in which hydrogenation catalyst is disposed, and through whichhydrogenation reaction feed flows. The tube(s) are themselves disposedwithin a shell such that the shell carries temperature-control media(e.g., water, refrigerant, or another process stream) capable ofabsorbing heat from the hydrogenation reaction(s) taking place withinthe tubes. The fluid flowing through the shell and over the tube(s) mayalso or instead carry heat to the hydrogenation catalyst disposed withinthe tubes. For instance, the hydrogenation catalyst may periodically beregenerated by heating (discussed in more detail below), and suchheating may be carried out in situ in the hydrogenation reactor byproviding heat through a fluid flowing through the shell and over thetube(s).

The hydrogenation reaction zone includes a hydrogenation catalyst, inthe presence of which various reactions take place. Preferably, eachreactor in the hydrogenation reaction zone comprises a bed ofhydrogenation catalyst (i.e., a hydrogenation catalyst bed) disposedtherein.

The hydrogenation catalyst may comprise a hydrogenation metal performinga hydrogenation function supported on a support material. Thehydrogenation metal can be, e.g., Fe, Co, Ni, Ru, Rh, Pd, Ag, Re, Os,Ir, and Pt, and mixtures and combinations of one or more thereof. Pd isa particularly preferred hydrogenation metal according to anyembodiment. The concentration of the hydrogenation metal can be, e.g.,in a range from 0.001 wt % to 7.5 wt % (such as 0.01 wt % to 5.0 wt %),based on the total weight of the catalyst. Preferably, the metal ispresent in its fully reduced metal state (e.g., Pd⁰ as opposed to Pdoxide (Pd⁺² oxidation state)). The support material can beadvantageously an inorganic material, such as oxides, glasses, ceramics,molecular sieves, and the like. For example, the support material can beactivated carbon, Al₂O₃, Ga₂O₃, SiO₂, GeO₂, SnO, SnO₂, TiO₂, ZrO₂,Sc₂O₃, Y₂O₃, alkali metal oxides, alkaline earth metal oxides, andmixtures, combinations, complexes, and compounds thereof. Preferredsupports include Al₂O₃ and/or activated carbon. Hydrogenation catalystsaccording to any embodiment may further comprise an alkali or alkalineearth metal dopant (e.g., a sodium dopant) in amounts ranging from about0.1 to about 3 wt %, such as about 0.5 to 1.5 wt %. Furthermore, withoutwishing to be bound by theory, it is believed that the preferredhydrogenation reactions occur quickly in the presence of thehydrogenation metal. Therefore, it is highly desirable that thehydrogenation metal is preferentially distributed in the outer rim ofthe catalyst particles, i.e., the concentration of the hydrogenationmetal in the catalyst particle surface layer is higher than in the corethereof. Such rimmed catalyst can reduce the overall hydrogenation metalloading, reducing cost thereof, especially if the hydrogenation metalcomprises a precious metal such as Pt, Pd, Ir, Rh, and the like. The lowconcentration of hydrogenation metal in the core of the catalystparticle also leads to a lower chance of hydrogenation of cyclohexanone,which may diffuse from the surface to the core of the catalystparticles, resulting in higher selectivity of cyclohexanone in theoverall process.

It is believed that the catalyst surface can have different degrees ofadsorption affinity to the different components in the reaction mediasuch as phenol, cyclohexanone, cyclohexanol, 2-cyclohexenone,3-cyclohexenone, cyclohexylbenzene, and bicyclohexane. It is highlydesired that the catalyst surface has higher adsorption affinity tophenol, 2-cyclohexenone and 3-cyclohexenone than to cyclohexanone andcyclohexylbenzene. Such higher phenol, 2-cyclohexenone and3-cyclohexenone adsorption affinity will give phenol competitiveadvantages in the reactions, resulting in higher selectivity tocyclohexanone, lower selectivity of cyclohexanol, and lower conversionof cyclohexylbenzene, which are all desired in a process designed formaking cyclohexanone.

As noted, numerous reactions may take place in the hydrogenationreaction zone. The possibilities are generally complicated as comparedto conventional phenol hydrogenation reactions by virtue of the presenceof cyclohexanone and cyclohexylbenzene in the feed.

To further complicate matters, various impurities may be present in thehydrogenation feed (e.g., from one or more upstream processes inaccordance with the hydroalkylation, oxidation, and cleavage reactionprocesses described previously). For instance, the hydrogenation feedmay further comprise cyclohexanol and/or other oxygenated hydrocarboncompounds produced as byproducts of interactions between components inpreviously-described upstream processes, such as condensation reactionproducts.

Furthermore, certain light components, such as organic acids (e.g.,formic acid, acetic acid, propanoic acid, linear, linear branched andcyclic carboxylic acids comprising 5, 6, 7, or 8 carbon atoms such asbenzoic acid), N-containing compounds (e g, amines, imides, amides, NO₂—substituted organic compounds), and S-containing compounds (e.g.,sulfides, sulfites, sulfates, sulfones, SO₃, SO₂) may be present in thehydrogenation feed. Such light components, if contained in the reactionmixture in the hydrogenation reactor and allowed to contact thehydrogenation metal under the hydrogenation reaction conditions, maypoison the hydrogenation catalyst, leading to reduction of performanceor premature failure of the catalyst. The aforementioned lightcomponents (organic acids, N-containing compounds, and 5-containingcompounds) are therefore also referred to as catalyst poison components.To avoid catalyst poisoning, it is highly desirable that thehydrogenation feed comprises such catalyst poison components at lowconcentrations (such as 0 to 5000 ppm by weight each, preferably 0 to1000 ppm by weight each, such as 1 ppm by weight to 100 ppm by weight).

III.7 Pre-Hydrogenation Treatments

In view of the foregoing, any embodiment include treating one or moreof: (1) a hydrogen feed stream; and (2) a hydrogenation feed streamcomprising phenol, cyclohexanone, and cyclohexylbenzene supplied to ahydrogenation reaction zone, using one or more pre-hydrogenationtreatments in order to, e.g., (i) remove impurities, (ii) suppressundesired side reactions, and/or (iii) improve catalyst life and/orselectivity to the desired cyclohexanone product, among other reasons.In other words, hydrogenation feed treatments discussed herein may beapplied to a phenol-containing process stream at any point between (1)initial separation of the cleavage effluent into at least thephenol-containing stream; and (2) provision of the phenol-containingprocess stream to a hydrogenation reaction zone. In any embodiment, suchtreatments need not be applied to a hydrogenation stream, but also orinstead may be applied directly to a hydrogenation reaction zone itself(e.g., a compound provided as a pre-hydrogenation treatment may besupplied via one or more feed streams provided to the hydrogenationreaction zone separately from the hydrogenation feed stream).

Pre-hydrogenation treatment according to any embodiment includes passinga hydrogenation feed stream through one or more sorbents and/or one ormore additional distillation columns (referred to herein as “posteriorsorbents” and “posterior distillation columns,” indicating downstreamrelationship relative to the separation of cleavage effluent or otherstream into at least a phenol-containing stream). Such posterior sorbentand/or posterior distillation treatment may be instead of or in additionto the treatment of cleavage reaction product to remove catalyst poisoncomponents such as S-containing components prior to separation of thecleavage reaction product, discussed above.

Pre-hydrogenation treatment according to other embodiments may also orinstead include the addition of basic chemical agents to thehydrogenation feed stream in order to condition the hydrogenationcatalyst (e.g., by tuning the acidity of the catalyst). Suitable basicchemical agents include one or more bases selected from the groupconsisting of amines, soluble inorganic bases, and mixtures thereof.Such chemical agents are added to the hydrogenation feed as solutions,or are dissolved into the feed (as opposed to passing the feed throughsolid-phase basic ion exchange resin, per the previous description).Alternatively or in addition, such chemical agents may be provideddirectly to the hydrogenation reaction zone separately from thehydrogenation feed. Preferred examples of amine chemical agents includealkylamines, such as the primary, secondary, and tertiary alkylamines,cyclic amines, etc., regardless of carbon type or chain length (e.g.,methylamine, monoethanolamine, dimethylamine as particular examples).Preferred examples of inorganic base chemical agents include alkalimetal and alkaline earth metal compounds (e.g., NaOH and Na₂CO₃ inparticular). Without wishing to be bound by theory, it is believed thatsuch agents may condition the acidity inherent in hydrogenationcatalysts according to any embodiment. For instance, varioushydrogenation catalyst supports (e.g., Al₂O₃, activated carbon) containvarying degrees of acidic sites; addition of a basic chemical agent to ahydrogenation feed may result in such basic chemical agents reactingwith the catalyst's acidic sites, so as to reduce the acidity of thecatalyst. This may improve catalyst life and/or phenol conversion rate,and/or cyclohexanone selectivity. Furthermore, addition of such basicchemical agents (e.g., Na₂CO₃) may lower the selectivity to cyclohexanoland may inhibit the undesired hydrogenation of cyclohexylbenzene presentin the hydrogenation feed. Such chemical agents are preferably suppliedto the hydrogenation feed stream and/or hydrogenation reaction zone inamounts ranging from about 0.01 to 5 wt %, preferably 0.01 to 0.1 wt %,most preferably about 0.03 to 0.07 wt %, on the basis of hydrogenationfeed (exclusive of hydrogen and any inert fluids that may be provided tothe hydrogenation reaction zone with the hydrogenation feed).

Pre-hydrogenation treatment according to yet further embodiments also orinstead includes providing water to one or more of a hydrogenation feedstream or the hydrogenation reaction zone. Water may be added in amountsranging from about 0.1 to 20 wt %, on the basis of hydrogenation feedprovided to the hydrogenation reaction zone (exclusive of hydrogen andany inert fluids provided to the hydrogenation reaction zone). In anyembodiment, water is added in relatively low amounts (e.g., preferably0.1 to 3 wt %, such as 1 to 3 wt %), whereas in other embodiments, wateris added in relatively high amounts (e.g., preferably 5 to 20 wt %, suchas 6 to 15 wt %). In any embodiment where water is added in relativelyhigh amounts, the amount of water added is based upon the phenol presentin the hydrogenation feed. For instance, phenol may be added at a waterto phenol weight ratio of at least 0.10, more preferably at least 0.12,such as at least 0.15. Addition of water according to any embodiment mayserve multiple useful purposes. For instance, it may suppress variousundesired side reactions. In particular, it may suppress the undesiredside reaction of hydrogenation of cyclohexylbenzene.

It is hypothesized that a small amount of water may form a hydrophiliclayer on the hydrogenation catalyst surface, preventing the diffusion ofcyclohexylbenzene to the catalyst surface (and thereby inhibiting thecatalyzed hydrogenation of cyclohexylbenzene), while permitting the morepolar phenol compounds to continue to diffuse to the catalyst, where thephenol is hydrogenated. Water may also suppress the formation ofcondensation products from components in the hydrogenation feed (e.g.,aldols and the like). Since water is formed as a product of suchequilibrium-driven reactions, the presence of water may suppress theoccurrence of such reactions. This is advantageous insofar as thenon-water condensation products may adsorb to the hydrogenationcatalyst, plugging sites that could otherwise be used by phenol to behydrogenated, and thereby significantly decreasing the conversion ofphenol over the hydrogenation catalyst as time passes.

It should also be noted that in any embodiment, a chemical agent (e.g.,Na₂CO₃) may be supplied to the hydrogenation feed stream and/or thehydrogenation reaction zone as an aqueous solution. The aqueous solutionmay be provided in amounts sufficient to provide the aforementionedamounts of water to the hydrogenation reaction zone, thereby effectivelycombining two treatment methods.

Pre-hydrogenation treatment according to further embodiments includesdiluting a hydrogen feed stream to the hydrogenation reaction zone withan inert fluid, such as nitrogen, methane, steam, or any other substancecapable of controlling the hydrogenation reaction selectivity byreducing or diminishing the hydrogen partial pressure in the reactionzone. Such hydrogen partial pressure will vary with reactor operatingpressure. A convenient way to represent the hydrogen partial pressureeffect on the hydrogenation process is to operate at a desired hydrogento phenol molar ratio, which may range from about 0.1 to 6.0 (preferablyabout 2.0 to about 4.0) moles hydrogen to moles phenol fed to thehydrogenation reaction zone.

Yet further embodiments include temporarily introducing one or morehydrogenation catalyst inhibitors to the hydrogenation feed and/or thehydrogenation reaction zone (that is, continuously introducing thecatalyst inhibitor for only a limited period of time that is shorterthan the period of time during which hydrogenation feed is continuouslyintroduced to the hydrogenation reaction zone). A “catalyst inhibitor”as used herein should be understood as any compound that is capable oftemporarily and reversibly suppressing the activity of a hydrogenationcatalyst (e.g., by reversibly adsorbing to active hydrogenation metalsites on the catalyst). A catalyst inhibitor is distinct from a catalystpoison component insofar as the catalyst inhibitor's effect may bereadily controlled so as to be temporary and reversible during normalprocess conditions simply by ceasing the supply of the catalystinhibitor. For instance, the catalyst inhibitor CO may adsorb ontoactive metal sites on the hydrogenation catalyst, but be readilydesorbed by other components of the hydrogenation feed and/or hydrogenfeed. Thus, once continuous flow of CO to the hydrogenation reactionzone stops, the remaining CO will desorb, restoring catalyst activity.Such a temporary effect is advantageous during start-up of a processwith fresh catalyst (e.g., freshly-reduced, activated catalyst), whichmay be hyper-active. Such highly active catalyst may promote ahigher-than-desired phenol hydrogenation rate, which could lead toexcessive, difficult to control, heat release. Excessively high catalystactivity may also cause formation of undesired byproducts (e.g., viahydrogenation of cyclohexanone to cyclohexanol).

Accordingly, processes according to any embodiment include continuouslyintroducing hydrogen, a hydrogenation feed, and a catalyst inhibitor tothe hydrogenation reaction zone (e.g., as a separate feed or as part ofthe hydrogenation and/or hydrogen feed) during a first time period so asto inhibit activity of a hydrogenation catalyst disposed within thehydrogenation reaction zone (e.g., by adsorbing onto one or more activehydrogenation metal sites on the catalyst), and subsequently ceasing theintroduction of the catalyst inhibitor to the hydrogenation reactionzone so as to stop the inhibition of hydrogenation catalyst activity(e.g., by allowing the catalyst inhibitor to desorb from the one or moreactive hydrogenation metal sites on the catalyst), and thereaftercontinuing to introduce the hydrogen and the hydrogenation feed into thehydrogenation reaction zone during a second time period subsequent tothe first time period. Suitable catalyst inhibitors include CO, and,potentially, H₂S at low levels. Preferably, the catalyst inhibitor isCO. Catalyst inhibitor is fed as a vapor, in a range from 0 vol % to 1vol % on the basis of hydrogen fed to the hydrogenation reaction zone,preferably 1 to 100 ppm by volume (on the basis of hydrogen fed to thehydrogenation reaction zone).

III.8 Catalyst Regeneration/Rejuvenation

Notwithstanding the use of the foregoing pre-hydrogenation treatments,hydrogenation catalyst activity may still decrease as normal operationof a hydrogenation reaction zone progresses over time. Accordingly, anyembodiment provide for methods for regenerating and/or rejuvenating thehydrogenation catalyst disposed within one or more hydrogenationreactors of a hydrogenation reaction zone.

Methods according to some such embodiments advantageously includeon-stream catalyst regeneration or rejuvenation (i.e., regeneration orrejuvenation that takes place while hydrogenation feed is provided tothe hydrogenation reaction zone, so as to allow for the desired phenolhydrogenation while the catalyst is being regenerated). A particularexample of such a process is mixed-phase operation of the hydrogenationreaction, meaning that the hydrogenation reaction medium (comprisingunreacted hydrogenation feed and any products and byproducts formedwithin the reaction zone) contacting the hydrogenation catalyst withinthe hydrogenation reaction zone is in mixed liquid and vapor phase. Itis believed that when at least a portion of the hydrogenation feedcontacting the hydrogenation catalyst is maintained in liquid phase, theliquid phase portion of the feed serves as a liquid wash, which removesimpurities (e.g., hydrocarbon and/or oxygenate impurities, catalystpoisons, and the like) that have adsorbed or absorbed onto thehydrogenation catalyst (either on active metal sites or on the support,so as to block phenol's access to active metal sites). The impuritiesmay be removed by physical effects and/or chemical interaction with thepartially liquid-phase flow (e.g., the liquid may displace theimpurities, and/or the impurities may be at least partially soluble inthe liquid-phase reaction medium contacting the catalyst bed, such thatthe impurities are dissolved within the passing liquid). In order toprovide this washing effect, it is preferred that liquid hold-up and/orliquid flux through a bed of hydrogenation catalyst be maintained at orabove certain levels. Thus, during mixed-phase operation according toany embodiment, liquid holdup in a hydrogenation reaction zone (e.g., ahydrogenation reactor) should be maintained at greater than or equal to1 vol %, based upon the available void volume in the hydrogenationcatalyst bed within the hydrogenation reaction zone. Preferably, liquidmass flux through the hydrogenation catalyst bed is at least 2 kg/m²s.Where the hydrogenation reaction zone comprises multiple hydrogenationcatalyst beds (e.g., where the hydrogenation reaction zone comprisesmultiple hydrogenation reactors, and/or comprises one or moreshell-and-tube hydrogenation reactors with multiple tubes), the liquidmass flux through each catalyst bed is at least 2 kg/m²s. Liquid massflux is determined based upon the cross-sectional area through which theliquid passes (e.g., the cross-sectional area of the catalyst bed, or,where the catalyst bed is disposed within a hydrogenation reactor, thecross-sectional area of the reactor).

Generally, mixed-phase operation is obtained by adjusting and/ormaintaining hydrogenation reaction conditions (particularly temperatureand/or pressure). It is well within the ability of an ordinarily skilledartisan to determine suitable combinations of temperature and pressurefor mixed-phase operation with minimal experimentation. In particular,an ordinarily skilled artisan will recognize that temperature andpressure are co-dependent (that is, the pressure at which mixed-phaseconditions exist depends in part upon the temperature in thehydrogenation reaction zone, and vice-versa). Thus, numerous differentcombinations of temperature and pressure to arrive at mixed-phaseconditions are possible. In general, for a given temperature that isheld constant, higher pressure will be needed to move from vapor tomixed-phase. And, for a given pressure that is held constant, lowertemperature will be needed to move from vapor to mixed-phase. And, ofcourse, a combination of higher pressure and lower temperature may alsobe used to move reaction conditions from vapor phase to mixed-phase.

In general, mixed-phase conditions will exist with temperature withinthe range of 25° C. to 250° C., and pressure within the range of 0 kPa(gauge) to 2000 kPa (gauge), while vapor phase operation will includetemperature within the range from 100° C. to 300° C. and pressure withinthe range from 0 kPa (gauge) to 2000 kPa (gauge). For temperatureswithin the lower end of a given range, pressure may correspondingly bein the lower end of the range. Conversely, when temperature is at thehigher end of the range, it will be necessary for pressure to be at thehigher end of the range so as to ensure mixed-phase operation. Forexample, for pressures of 175 kPa (gauge) or less, temperature in therange of 150 to 200° C. results in vapor-phase operation. But atpressures of around 800 kPa (gauge), temperature may range from 100° C.to 200° C. to enable mixed-phase operation. As another example, vaporphase conditions may include about 70 kPa (gauge) and 165° C. to 180°C., while mixed-phase conditions at 70 kPa (gauge) would exist at 120°C. In some particular embodiments, mixed-phase conditions are maintainedby maintaining temperature within the range of 100° C. to 200° C., andmaintaining pressure at 800 kPa (gauge) or less, while adjusting theconditions to simultaneously maintain mixed-phase operation and alsomaintaining an acceptable hydrogenation reaction rate.

Mixed-phase operation as described above may be maintained as the normaloperating condition of the hydrogenation reaction. Thus, methodsaccording to any embodiment include continuously providing hydrogen andhydrogenation feed comprising phenol, cyclohexanone, andcyclohexylbenzene to a hydrogenation reaction zone in which ahydrogenation catalyst bed is disposed, thereby maintaining a reactionmedium flowing through the hydrogenation catalyst bed within thehydrogenation reaction zone; and maintaining temperature and pressure inthe hydrogenation reaction zone such that the reaction medium flowingthrough the hydrogenation catalyst bed remains in mixed liquid and vaporphase.

In yet other embodiments, mixed-phase operation may be a temporarydeparture from standard operating conditions (either vapor or liquidphase operations, preferably a departure from standard vapor-phaseoperating conditions). In particular embodiments, the hydrogenationreaction is normally operated in vapor phase, with one or more temporarydepartures to operation in the mixed liquid- and vapor-phase so as toachieve a liquid washing effect. Thus, methods according to anyembodiment include (a) during a first period of time, flowing (i)hydrogen, and (ii) a vapor-phase hydrogenation feed comprising phenol,cyclohexanone, and cyclohexylbenzene through a hydrogenation catalystbed so as to hydrogenate at least a portion of the phenol in thevapor-phase hydrogenation feed to cyclohexanone, and further so as toform one or more hydrocarbon and/or oxygenate impurities that adsorb orabsorb onto at least a portion of the hydrogenation catalyst bed; and(b) during a second period of time subsequent to the first period oftime, flowing (i) hydrogen, and (ii) a mixed liquid- and vapor-phasehydrogenation feed comprising phenol, cyclohexanone, andcyclohexylbenzene through the hydrogenation catalyst bed so as tohydrogenate at least a portion of the phenol in the mixed liquid- andvapor-phase hydrogenation feed to cyclohexanone, and further so as toremove at least a portion of the one or more hydrocarbon and/oroxygenate impurities from the hydrogenation catalyst bed.

Methods according to yet further embodiments of temporary mixed-phaseoperation include: (a) during a first period of time; continuouslyproviding hydrogen and a hydrogenation feed to a hydrogenation reactionzone in which hydrogenation catalyst is disposed, thereby maintaining areaction medium flowing through the hydrogenation catalyst bed withinthe hydrogenation reaction zone, while maintaining initial temperatureand initial pressure conditions within the hydrogenation reaction zonesuch that the reaction medium is entirely in vapor phase during thefirst period of time; (b) adjusting the initial temperature conditions,the initial pressure conditions, or both, within the hydrogenationreaction zone to obtain liquid washing temperature and pressureconditions within the hydrogenation reaction zone, such that thereaction medium is in mixed liquid and vapor phase after the adjusting;and (c) during a second period of time subsequent to the first period oftime, maintaining the liquid washing temperature and pressure conditionswithin the hydrogenation reaction zone while continuously providing thehydrogen and the hydrogenation feed to the hydrogenation reaction zone,thereby maintaining the reaction medium flowing through thehydrogenation catalyst bed in mixed liquid and vapor phase.

In yet other embodiments, hydrogenation catalyst regeneration and/orrejuvenation may also or instead be carried out off-stream (that is, inthe absence of the provision of hydrogenation feed to a hydrogenationreactor within the hydrogenation reaction zone). Preferably, in suchembodiments, the hydrogenation reaction zone comprises multiplehydrogenation reactors configured such that, while one or more of thereactors are taken off-line (e.g., provision of hydrogenation feed tosuch reactors is halted), the remainder of the reactors remain in normaloperation (e.g., hydrogenation feed and hydrogen continue to be suppliedto the remainder of the reactors such that phenol hydrogenationcontinues to take place in the remainder of the reactors). Thisconfiguration may be effected by any suitable means, such as paralleloperation of the multiple hydrogenation reactors of such hydrogenationreaction zones, and/or by the use of a manifold to enable ahydrogenation feed to be selectively provided to any one or more of aplurality of hydrogenation reactors within the hydrogenation reactionzone.

Once taken out of service, a hydrogenation reactor can be subjected to apurging fluid that is preferably inert when contacted with thehydrogenation catalyst (e.g., any one or more of nitrogen, methane,steam, or a combination thereof). The purging fluid removes byproductsand other compounds adsorbed, absorbed, or otherwise trapped within theporous structure of the hydrogenation catalyst bed disposed within thatreactor. Also or instead, the hydrogenation catalyst may be regeneratedby conducting a controlled oxidative burn with dilute air so as tocombust hydrocarbons and/or oxygenates trapped within the hydrogenationcatalyst as CO, CO₂, and H₂O. Such dilute air may be generated by mixingair with diluent gases known to those skilled in the art. The catalystregenerated according to such embodiments is then purged to removeresidual oxygen, and is subsequently reduced by flowing a dilutehydrogen stream at process conditions sufficient to attain completereduction of the catalyst's active hydrogenation metals such as Pd (thatis, such metals are converted from their oxide states to their fullyreduced metal states). The reactor may then be placed back in service.

Preferably, once a reactor is placed in service in a hydrogenationreaction zone comprising multiple hydrogenation reactors in series, thenewly in-service reactor is placed in the tail-end of the multipleseries reactors. That is, the hydrogenation reactor subjected to theout-of-service rejuvenation/regeneration procedure just described (i.e.,the regenerated reactor) is preferably returned to service by providingthe effluent of the most down-stream hydrogenation reactor of thehydrogenation reaction zone to the regenerated reactor.

IV. Cyclohexanone-Containing Products

In any embodiment, the methods and/or systems described herein can beused to make cyclohexanone-containing products that are depleted in3-cyclohexenone. Such products can comprise, based on its total weight,at least 10 wt % of cyclohexanone; 0 to 90 wt % of cyclohexanol; and0.01 to 20 ppm of 3-cyclohexenone.

Preferably, the cyclohexanone-containing product is a high-puritycyclohexanone product comprising at least 99 wt % cyclohexanone, basedon the total weight of the cyclohexanone-containing product. Morepreferably, the high-purity cyclohexanone product comprises at least99.90 wt %, 99.94 wt %, 99.95 wt %, or even 99.99 wt % cyclohexanone.

The cyclohexanone-containing product can be a KA oil product comprisingcyclohexanol at any concentration in the range from 5 to 90 wt %, suchas from 10 to 80 wt %, from 20 to 70 wt %, from 30 to 60 wt %, or from40 to 50 wt %.

The cyclohexanone-containing product can comprise 3-cyclohexenone at aconcentration in the range from f1 to f2 ppm, based on the total weightof the cyclohexanone-containing product, where f1 and f2 can be,independently, 0.01, 0.05, 0.1, 0.05, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, aslong as f1<f2.

The cyclohexanone-containing product can comprise 2-cyclohexenone at aconcentration in the range from g1 to g2 ppm, based on the total weightof the cyclohexanone-containing product, where g1 and g2 can be,independently, 0.01, 0.05, 0.1, 0.05, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, aslong as g1<g2.

The cyclohexanone-containing product may further comprise one or moreadditional cyclohexanone impurities selected from the followingcompounds: benzene, cyclohexene, pentanal, cyclopentanol, cyclohexanol,and phenol. As used herein, a “cyclohexanone impurity” is any compoundother than cyclohexanone or water, which is typically acceptable incommercially available cyclohexanone-containing products in smallamounts. Water is desirably present in the cyclohexanone composition inamounts of 0.15 wt % or less, such as 0.1 wt % or less, or 0.05 wt % orless, based on total weight of the cyclohexanone-containing product.Preferably, the total amount of cyclohexanone impurities is 500 ppm byweight or less, more preferably 200 ppm by weight or less, mostpreferably 150 ppm by weight or less, or even 100 ppm by weight or less,each ppm by weight being based upon the total weight of thecyclohexanone-containing product.

The cyclohexanone-containing product may comprise any one or more, twoor more, three or more, or four or more of such cyclohexanoneimpurities. In particular embodiments, the cyclohexanone-containingproduct comprises one or both of pentanal and cyclopentanol each atconcentration of 200 ppm by weight or less, preferably 100 ppm by weightor less. Compositions of such embodiments may also, or instead, compriseone or both of cyclohexene and cyclohexanol each at concentration of 200ppm by weight or less, preferably 100 ppm by weight or less.

In any embodiment, the cyclohexanone-containing product may consist ofcyclohexanone, 2-cyclohexenone at the above described concentrations,3-cyclohexenone at the above described concentration, 0.15 wt % or less(preferably 0.1 wt % or less, most preferably 0.05 wt % or less) water,and 500 ppm by weight or less (preferably 200 ppm by weight or less,most preferably 100 ppm by weight or less) of one or more cyclohexanoneimpurities. The cyclohexanone impurities in such embodiments arepreferably selected from the group consisting of: benzene, cyclohexene,pentanal, cyclopentanol, cyclohexanol, 2-cyclohexenone, 3-cyclohexenone,and phenol. In any embodiment, the cyclohexanone impurities are selectedfrom the group consisting of: cyclohexene, pentanal, cyclopentanol, andcyclohexanol. Such compositions may consist of any one, two, three, orfour of the foregoing impurities. In particular embodiments, theimpurities consist of cyclohexene, pentanal, cyclopentanol, andcyclohexanol. In yet further particular embodiments, the impuritiesconsist of (i) cyclohexene, (ii) cyclopentanol or pentanal, and (iii)cyclohexanol.

With respect to each aforementioned cyclohexanone impurity in thecyclohexanone-containing products:

-   -   Benzene may be present in an amount ranging from 0 to 20 ppm by        weight. For instance, benzene may be present at 0 ppm by weight        to 5 ppm by weight, preferably 0 ppm by weight to 2.5 ppm by        weight.    -   Cyclohexene may be present in an amount ranging from 0 to 20 ppm        by weight. For instance, cyclohexene may be present at 0 ppm by        weight to 15 ppm by weight, such as 2.5 ppm by weight to 15, or        5 ppm by weight to 10 ppm by weight.    -   Pentanal may be present in an amount ranging from 0 to 200 ppm        by weight. For instance, pentanal may be present at 0 ppm by        weight to 100 ppm by weight, such as 1 ppm by weight to 80 ppm        by weight, potentially 3 ppm by weight to 60 ppm by weight.    -   Total lights (including benzene, cyclohexene, pentanal,        cyclopentanone, and pentanal) may be preferably present in an        amount ranging from 10 to 2000 ppm by weight, more preferably        from 10 to 1000 ppm by weight, still more preferably 20 to 500        ppm by weight, still more preferably 20 to 400 ppm by weight.    -   Cyclopentanol may be present in an amount ranging from 0 to 80        ppm by weight. For instance, cyclopentanol may be present at 10        ppm by weight to 50 ppm by weight, such as 15 to 40 ppm by        weight, or 20 to 35 ppm by weight.    -   Cyclohexanol may be present in an amount ranging from 0 to 1000        ppm by weight. For instance, cyclohexanol may be present at 0        ppm by weight to 800 ppm by weight, such as 10 ppm by weight to        600 ppm by weight, for instance 50 ppm by weight to 500 ppm by        weight, or 100 ppm by weight to 400 ppm by weight.

In any embodiment, any one or more of these cyclohexanone impurities mayhave been generated in situ during a process for making cyclohexanone(i.e., they were not added from an external source). For instance, anyone or more of the cyclohexanone impurities may have been formed duringthe phenol hydrogenation reaction. This is particularly likely forcyclohexanone impurities such as cyclohexanol, cyclohexene,2-cyclohexenone, 3-cyclohexenone, and water. Additionally, any traceamount of unreacted phenol left over from the hydrogenation reaction mayremain as a cyclohexanone impurity in any embodiment. Furthermore, inany embodiment, at least a portion of the cyclohexene may have beenproduced at least in part during distillation or other treatment of allor part of the phenol hydrogenation reaction effluent.

Further, in any embodiment all or at least part of the pentanal and/orcyclopentanol may be formed either before or after (i.e., upstream ordownstream of, respectively) hydrogenation of the hydrogenation feedcomprising cyclohexanone and phenol.

The cyclohexanone-containing product produced through the processesdisclosed herein may be used, for example, as an industrial solvent, asan activator in oxidation reactions and in the production of adipicacid, cyclohexanone resins, cyclohexanone oxime, caprolactam, andnylons, such as nylon-6 and nylon-6,6.

The phenol produced through the processes disclosed herein may be used,for example, to produce phenolic resins, bisphenol A, caprolactam,adipic acid, and/or plasticizers.

V. Composition of Matter Comprising Cyclohexylbenzene, Phenol,Cyclohexanone, and 3-Cyclohexenone

Another aspect of the present disclosure is a composition of mattercomprising 20 to 70 wt % of cyclohexylbenzene; 5 to 40 wt % of phenol; 5to 40 wt % of cyclohexanone; and 50 ppm to 5 wt % of 3-cyclohexenone.This composition of matter can be desirably produced from the CHB-route,as a mixture obtainable from the cleavage reactor, with or withoutaddition post-cleavage treatment as described above. This composition ofmatter can be advantageously used as the feed mixture for producingcyclohexanone-containing products depleted in 2-cyclohexenone and3-cyclohexenone as described above.

Thus, the composition of matter can comprise 3-cyclohexenone at aconcentration in the range from h1 to h2 ppm by weight, based on thetotal weight of the composition, where h1 and h2 can be, independently,50, 80, 100, 200, 400, 500, 600, 800, 1000, 2000, 4000, 5000, 6000,8000, 1×10⁴, 2×10⁴, 4×10⁴, 5×10⁴, 6×10⁴, 8×10⁴, 1×10⁵, 2×10⁵, 4×10⁵,5×10⁵, 6×10⁵, 8×10⁵, 1×10⁶, 2×10⁶, 4×10⁶, 5×10⁶, as long as h1<h2.Preferably h1=50, h2=2000. More preferably h1=100, h2=1000.

The composition of matter can further comprise 2-cyclohexenone at aconcentration in the range from j1 to j2 ppm by weight, based on thetotal weight of the composition, where j1 and j2 can be, independently,50, 80, 100, 200, 400, 500, 600, 800, 1000, 2000, 4000, 5000, 6000,8000, 1×10⁴, 2×10⁴, 4×10⁴, 5×10⁴, 6×10⁴, 8×10⁴, 1×10⁵, 2×10⁵, 4×10⁵,5×10⁵, 6×10⁵, 8×10⁵, 1×10⁶, 2×10⁶, 4×10⁶, 5×10⁶, as long as j1<j2.Preferably j1=50, j2=2000. More preferably j1=100, j2=1000.

Thus, the composition of matter can comprise cyclohexylbenzene at aconcentration in the range from k1 to k2 ppm by weight, based on thetotal weight of the composition, where k1 and k2 can be, independently,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70, as long as k1<k2.Preferably k1=30, k2=65. More preferably k1=40, k2=60.

Thus, the composition of matter can comprise cyclohexanone at aconcentration in the range from m1 to m2 ppm by weight, based on thetotal weight of the composition, where m1 and m2 can be, independently,5, 10, 15, 20, 25, 30, 35, or 40, as long as m1<m2. Preferably m1=10,m2=35. More preferably m1=15, m2=30.

Thus, the composition of matter can comprise phenol at a concentrationin the range from n1 to n2 ppm by weight, based on the total weight ofthe composition, where n1 and n2 can be, independently, 5, 10, 15, 20,25, 30, 35, or 40, as long as n1<n2. Preferably n1=10, n2=35. Morepreferably n1=15, n2=30.

The present invention is further illustrated by the followingnon-limiting examples.

EXAMPLES

Examples of the separation and hydrogenation processes and/or systemsaccording to some particular embodiments are illustrated in the attacheddrawings and described in detail below. It should be understood thatprocesses and/or systems shown in the schematic, not-to-scale drawingsare only for the purpose of illustrating the general material flows andgeneral operating principles of particular embodiments in accordancewith these illustrations. To simplify illustration and description, someroutine components, such as pumps, valves, reboilers, pressureregulators, heat exchangers, recycling loops, condensers, separationdrums, sensors, rectifiers, fillers, distributors, stirrers, motors, andthe like, are not shown in the drawings or described herein. One havingordinary skill in the art, in light of the teachings herein, can addthose components where appropriate. While the material flow direction inall hydrogenation reactors illustrated in the examples are from top tobottom, it is also possible to run streams from bottom to top in thesereactors.

For Examples 2-5 below, exemplary but non-limiting first feed mixture(203, 303, 403, and 503, respectively) can desirably comprise: 20 to 70(preferably 40 to 60) wt % of cyclohexylbenzene, 5 to 40 (preferably 15to 30) wt % of phenol, 5 to 40 (preferably 15 to 30) wt % ofcyclohexanone, and 0 to 20 (preferably 0-10) wt % of all othercomponents combined (e.g., water, light acids, and the like) includingabout 30 ppm by weight to 1 wt % (preferably 50 to 5000 ppm by weight,more preferably 50 to 1000 ppm by weight) of 3-cyclohexenone and/or2-cyclohexenone.

Example 1

A spinning band distillation (“SBD”) was performed for a feed mixtureconsisting of 97 wt % cyclohexanone, 1 wt % cyclohexanol, 1 wt %3-cyclohexenone, and 1 wt % 2-cyclohexenone, using an SBD instrument(model M690) available from B/R Instruments, which has an address at9119 Centreville Road Easton, Md. 21601 USA. The SBD instrument includeda stainless steel band set to 2000 rpm, which gave 15 stages ofseparation. The pressure was 78 mm Hg (10 kPa absolute pressure) and thepot temperature was 91° C. The reflux ratio was 30:1. A total of fourfractions were taken from the distillation operation, labelled FractionNos. 1 to 4, respectively. Fraction No. 5 corresponds to the residual inthe pot after all four fractions were taken. The starting feed mixturewas labelled Fraction No. 0. Each fraction was measured for theconcentrations of the four compounds. Concentration data ofcyclohexanol, 2-cyclohexenone, and 3-cyclohexenone are reported inFIG. 1. As can be seen from FIG. 1, concentrations of 3-cyclohexenone inall Fraction Nos. 0, 1, 2, 3, 4, and 5 are substantially the same, andremain very close to the beginning concentration in the feed mixture ofabout 1 wt %. Based on these results, cyclohexanone and 3-cyclohexenonecannot be separated by distillation and have a relative volatility thatis very close to 1. On the other hand, with respect to 2-cyclohexenone,its concentration increased gradually from Fraction No. 0 to FractionNos. 1, 2, 3, 4, and eventually reached the highest in Fraction No. 5,which is significantly higher than its concentration in the initial feedmixture. As such, 2-cyclohexenone can be separated from cyclohexanone bydistillation.

Example 2 (Comparative)

FIG. 2 schematically illustrates a process/system 201 operating toproduce cyclohexanone from a first feed mixture comprisingcyclohexylbenzene, phenol, cyclohexanone, water, light acids, and3-cyclohexenone. The first feed mixture stream 203 is fed into a firstdistillation column (also known as the primary fractionator in thepresent disclosure) 205 at a first feed mixture feeding location, wherea lower effluent stream 207 (withdrawn preferably in the vicinity of thebottom of column 205) comprising cyclohexylbenzene and other optionalheavy components is produced. Stream 207 can be further separated toobtain a substantially pure stream of cyclohexylbenzene, which can berecycled to an upstream oxidation reactor (not shown) wherecyclohexylbenzene is oxidized to form cyclohexylbenzene hydroperoxide.From column 205, a middle effluent 209 is drawn at a middle effluentlocation above the first feed mixture location, but below the top ofcolumn 205. Stream 209, comprising cyclohexanone, phenol, cyclohexanol,3-cyclohexenone, optionally 2-cyclohexenone, optionally bicyclohexane,and optionally cyclohexylbenzene, is then fed into a hydrogenationreactor 213 together with a stream of hydrogen 211. In the presence of abed of hydrogenation catalyst installed inside reactor 213,2-cyclohexenone, 3-cyclohexenone, and phenol undergo hydrogenationreactions to form cyclohexanone, cyclohexanone undergoes hydrogenationto form cyclohexanol, and the optional cyclohexylbenzene, if present,undergoes hydrogenation to form bicyclohexane.

Hydrogenation of 2-cyclohexenone and 3-cyclohexenone are believed to bemuch faster than phenol hydrogenation under typical phenol hydrogenationconditions in the presence of the phenol hydrogenation catalyst. Assuch, the hydrogenation reactor effluent (also known as hydrogenatedmixture) 215 comprises cyclohexanone and cyclohexanol at higherconcentrations than stream 209, phenol at a reduced concentration thanstream 209, and optional cyclohexylbenzene and bicyclohexane, and issubstantially free of 2-cyclohexenone and 3-cyclohexenone. Stream 215 isrecycled back to the first distillation column 205 at a first recyclestream location no more than 5 theoretical stages above the first middleeffluent location. Above the first recycle stream location, a firstupper effluent 217 is produced (preferably at a location in the vicinityof the top of column 205). Stream 217 comprises cyclohexanone,cyclohexanol, water, hydrogen, and other light components such as lightacids and is substantially free of phenol. Stream 217 is then suppliedto a second distillation column 219, where it is separated to obtain alight component-rich upper effluent stream 221 comprising water,hydrogen, and light acids, and a cyclohexanone-rich lower effluentstream 223 comprising cyclohexanone and cyclohexanol. Stream 223 is thenfed into a third distillation column 225, where it is separated into acyclohexanone upper effluent stream 227 and a lower effluent stream 229.Stream 227 can comprise cyclohexanone at a purity of higher than 90 wt%, preferably higher than 95 wt %, more preferably higher than 99 wt %.Stream 229 can comprise cyclohexanol at any concentration depending onthe degree of separation in the third distillation column, butpreferably in the range from 30 to 90 wt %, more preferably from 40 to60 wt %. Streams 227 and 229 can be delivered to product storage andused for downstream applications such as productions of caprolactam,adipic acid, and the like.

As the results in Example 1 demonstrated, conventional distillationcannot completely separate a mixture of cyclohexanone and3-cyclohexenone. The concentration of 3-cyclohexenone in the mixture atthe first middle effluent location is substantial. While some of thematerial in recycle stream 215 travels downward to absorb a portion ofthe 3-cyclohexenone traveling upward from the first middle effluentlocation, the short distance of no more than 5 stages between the firstmiddle effluent location and the recycle location is insufficient tosuppress substantially all 3-cyclohexenone from reaching above therecycle location. Thus, the process of FIG. 2 is highly likely to resultin the presence of 3-cyclohexenone in the first upper effluent stream217, and eventually in streams 223, 227, and 229. Such likelihood iseven higher when phenol conversion in the hydrogenation reactor 213 ishigh and the total quantity of liquid recycled to column 201 via stream215 is therefore small.

A computer-based steady state process simulation was conducted for theprocess of 201 using Schneider Electric Software SimSci Pro/II(available from Schneider Electric Software having an address at 26561Rancho Parkway, South Lake Forest, Calif. 92630, U.S.A.) to quantify theamount of 3-cyclohexenone in the product. 3-cyclohexenone conversion tocyclohexanone in phenol hydrogenation was assumed to be 100%. Phenolconversion was assumed to be 80%. The first recycle stream location wastwo stages above the first middle effluent location. The results aregiven below. Clearly, the concentration of 3-cyclohexenone in thecyclohexanone product (stream 227) was reduced by only a smallpercentage compared to the feed stream (stream 203). The highconcentrations of 3-cyclohexenone in both streams 227 and 229 may renderthem unsuitable for intended uses.

Concentration of 3- Stream cyclohexenone (ppm) Feed Stream (Stream 203)104 Cyclohexanone Product (Stream 227) 85 KA Oil Product (Stream 229) 33

Example 3 (Inventive)

FIG. 3 schematically illustrates a process/system 301 operating toproduce cyclohexanone from a first feed mixture comprisingcyclohexylbenzene, phenol, cyclohexanone, water, light acids,2-cyclohexenone, and 3-cyclohexenone. The first feed mixture stream 303is fed into a first distillation column (aka “primary fractionator”) 305at a first feed mixture feeding location, where a lower effluent stream307 (preferably in the vicinity of the bottom of column 305) comprisingcyclohexylbenzene and other optional heavy components is produced.Stream 307 can be further separated to obtain a substantially purestream of cyclohexylbenzene, which is then recycled to an upstreamoxidation reactor (not shown) where cyclohexylbenzene is oxidized toform cyclohexylbenzene hydroperoxide. From column 305, a first uppereffluent 309 is drawn at a first upper effluent location above the firstfeed mixture location, preferably in the vicinity of the top of column305. Stream 309, comprising cyclohexanone, phenol, cyclohexanol,2-cyclohexenone, 3-cyclohexenone, and optionally cyclohexylbenzene andbicyclohexane, is then fed into a hydrogenation reactor 313 togetherwith a stream of hydrogen 311. In the presence of a bed of hydrogenationcatalyst installed inside reactor 313, 2-cyclohexenone, 3-cyclohexenone,and phenol undergo hydrogenation reactions to form cyclohexanone,cyclohexanone undergoes hydrogenation to form cyclohexanol, and theoptional cyclohexylbenzene, if present, undergoes hydrogenation formbicyclohexane. Because hydrogenation of 2-cyclohexenone and3-cyclohexenone are much faster than phenol hydrogenation under typicalphenol hydrogenation conditions in the presence of the phenolhydrogenation catalyst, the hydrogenation reactor effluent 315 comprisescyclohexanone and cyclohexanol at higher concentrations than stream 309,phenol at a reduced concentration than stream 309, and optionallycyclohexylbenzene and bicyclohexane, and is depleted in (preferablysubstantially free) of 2-cyclohexenone and 3-cyclohexenone because bothare substantially converted to cyclohexanone. Stream 315 is supplied toa second distillation column 317, where a cyclohexanone-rich uppereffluent stream 323 (preferably at a location in the vicinity of the topof column 317) and a phenol-rich lower effluent stream 321 are obtained(preferably at a location in the vicinity of the bottom of column 317).A hydrogen stream 319 is preferably (though not required to be) suppliedto the second distillation column 317 (preferably at a location in thevicinity of the bottom of the column). Hydrogen gas travelling upwardalong column 317 facilitates the separation of phenol fromcyclohexanone/cyclohexanol and leads to energy savings in the process.Stream 321, comprising cyclohexanone at a concentration lower thanstream 315, phenol at a concentration higher than stream 315, andoptional cyclohexylbenzene and bicyclohexane, depleted in (preferablysubstantially free of) 2-cyclohexenone and 3-cyclohexenone, is recycledback to the first distillation column 305 at a second feeding locationhigher than the first feeding location and lower than the first uppereffluent location. Alternatively, stream 321 may be recycled in itsentirety to the hydrogenation reactor 313. If cyclohexylbenzene ispresent in stream 309, doing so would result in accumulation ofbicyclohexane in stream 321, which can be undesirable. Alternatively,one can recycle a portion of stream 321 to the hydrogenation reactor,and another portion to the first distillation column as described above.

Stream 323, comprising cyclohexanone, cyclohexanol, water, and otherlights such as light acids and hydrogen, depleted of 2-cyclohexenone and3-cyclohexenone and preferably substantially free of 2-cyclohexenone and3-cyclohexenone, is then fed into a third distillation column 325, whereit is separated into an light component-rich upper effluent stream 327comprising hydrogen, water, light acids, and the like, and acyclohexanone-rich lower effluent stream 329. Stream 327 can be furtherseparated (not shown) to obtain a stream of hydrogen, which can berecycled to the hydrogenation reactor 313 as at least a part (preferablythe entirety) of the hydrogen stream 311 supplied into the hydrogenationreactor. Alternatively or in addition, one could also choose to separatestream 323 before it is fed into column 325 via high pressure separationdrum as in conventional hydro-processing to obtain a stream of hydrogen,which can be supplied to the hydrogenation reactor.

Stream 329 is then fed into a fourth distillation column 331, where itis separated into a cyclohexanone upper effluent stream 333 and a lowereffluent stream 335. Stream 333 can comprise cyclohexanone at a purityof higher than 99 wt %, preferably higher than 99.5 wt %, morepreferably higher than 99.9 wt %. Stream 329 may comprise2-cyclohexenone and/or 3-cyclohexeneone, each independently at aconcentration in the range from 0.01 to 20 (preferably 0.01 to 10 ppm,more preferably 0.01 to 5 ppm, still more preferably 0.01 to 1) ppm byweight, based on the total weight of stream 335. Stream 335 can comprisecyclohexanol at any concentration depending on the degree of separationin the fourth distillation column, but preferably in the range from 0 to90 wt %, more preferably from 10 to 60 wt %. Streams 333 and 335 can bedelivered to product storage and used for downstream applications suchas productions of caprolactam, adipic acid, and the like. Stream 335, ifcontaining cyclohexanol at substantial quantity, can be either sold andused as a KA oil product, or dehydrogenated to make an additionalquantity of high-purity cyclohexanone.

In FIG. 3, a single first upper effluent 309 comprising phenol,cyclohexanone, cyclohexanol, 2-cyclohexenone, 3-cyclohexenone, and lightcomponents is drawn from column 305. Alternatively, two upper effluentmay be drawn from column 305: a first upper effluent, preferably liquid,comprising cyclohexanone, phenol, 2-cyclohexenone, 3-cyclohexenone, andcyclohexanol and substantially free of water and other light components,and a second upper effluent comprising cyclohexanone, water, and otherlight components. The second upper effluent, preferably withdrawn at alocation in the vicinity of the top of column 305, can be separated toobtain (i) a cyclohexanone-rich stream, which is then recycled to alocation preferably in the vicinity of the top of column 305, and (ii) alight component stream, which can be further treated and disposed aswaste. The first upper effluent is then fed into the hydrogenationreactor as stream 309.

In FIG. 3, stream 321 is shown to be recycled in its entirety to column305. Alternatively, one can split this stream into two fractions, onerecycled to the column 305 as shown, the other to the hydrogenationreactor (not shown), to increase the overall conversion of phenol in thehydrogenation reactor. While theoretically it is possible to recyclestream 321 in its entirety to the hydrogenation reactor, doing so canresult in the accumulation of heavy components such as cyclohexylbenzeneand bicyclohexane in the hydrogenation reactor, which can reduce overallprocess efficiency and therefore can be undesirable.

In FIG. 3, two distillation columns 325 and 331 are utilized to separatestream 323 to obtain light component effluent stream 327, thecyclohexanone effluent stream 333 and the lower effluent stream 335(which can be a KA oil stream). Alternatively, the two columns can becombined into a single column, with the light component effluent drawnpreferably in the vicinity of the top, the lower effluent (e.g., a KAoil effluent) drawn preferably in the vicinity of the bottom, and thecyclohexanone effluent drawn at a location in between the two,preferably higher than the first feeding location.

Example 4 (Inventive)

FIG. 4 schematically illustrates a process/system 401 operating toproduce cyclohexanone from a first feed mixture comprisingcyclohexylbenzene, phenol, cyclohexanone, water, light acids,2-cyclohexenone, and 3-cyclohexenone. Process/system 401 comprises ahydrogenation zone 409 having a bed of hydrogenation catalyst installedinside the first distillation column 407. The first feed mixture stream403 is fed into a first distillation column 407 at a first feed mixturefeeding location below the hydrogenation zone 409. As shown in FIG. 4, ahydrogen stream 405 is supplied to the first distillation column at alocation below the hydrogenation zone and above the first feed location,although in addition or instead hydrogen stream 405 can be supplied at alocation below the first feeding location as well. Preferably in thevicinity of the bottom of column 407, a lower effluent stream 411comprising cyclohexylbenzene and other optional heavy components isobtained. The location of the hydrogenation zone 409 is chosen such thathydrogen, water, other light components, cyclohexanone, cyclohexanol,and phenol enter into the hydrogenation zone. Preferably only minoramount of or no cyclohexylbenzene (e.g., at most 5% of allcyclohexylbenzene in feed mixture stream 403) enters the hydrogenationzone. The height of the hydrogenation zone, the hydrogenation catalyst,the hydrogenation conditions, and the length and condition of the columnportion above the hydrogenation zone are chosen such that the overallconversion of phenol in the hydrogenation zone is generally in the rangefrom 90% to 100%, preferably above 99%, in column 407. Similarly,because 2-cyclohexenone and 3-cyclohexenone hydrogenate at much higherrate than phenol, they are substantially completely converted. Thus, afirst upper effluent stream 413 substantially free of phenol,2-cyclohexenone and 3-cyclohexenone, and comprising cyclohexanone,cyclohexanol, water and other light components is obtained at a locationabove the hydrogenation zone (preferably from a location in the vicinityof the top of column 407).

Stream 413 is then fed into a second distillation column 415, where itis separated into a light component-rich upper effluent stream 417comprising hydrogen, water, light acids, and the like, and acyclohexanone-rich lower effluent stream 419. Stream 417 can be furtherseparated (not shown) to obtain a stream of hydrogen by means such ashigh-pressure separation drum used in conventional hydro-processingprocesses, which can be recycled to the first distillation column 407 asa part of the hydrogen stream 405 supplied into column 407.

Stream 419 is then fed into a fourth distillation column 421, where itis separated into a cyclohexanone-rich upper effluent stream 423 and alower effluent stream 425. Stream 423 can comprise cyclohexanone at apurity of higher than 99 wt %, preferably higher than 99.5 wt %, morepreferably higher than 99.9 wt %. Stream 425 can comprise cyclohexanolat any concentration, depending on the degree of hydrogenation carriedout in the hydrogenation zone, but preferably in the range from 0 to 90wt %, more preferably from 10 to 40 wt %. Streams 423 and 425 can bedelivered to product storage and used for downstream applications suchas productions of caprolactam, adipic acid, and the like. Because stream413 is depleted in 2-cyclohexenone and 3-cyclohexenone and preferablysubstantially free of both, streams 419, 423, and 425 are likewisedepleted in both and preferably substantially free of both. Stream 425,if containing cyclohexanol at substantial quantity, can be either soldand used as a KA oil product, or dehydrogenated to make additionalquantity of high-purity cyclohexanone.

In FIG. 4, two distillation columns 415 and 421 are utilized to separatestream 413 obtain light component effluent stream 417, thecyclohexanone-rich upper effluent stream 423 and the lower effluentstream 425 (which can be a KA oil stream). Alternatively, the twocolumns can be combined into a single column, with the light componenteffluent (preferably drawn in the vicinity of the top), the lowereffluent (e.g., a KA oil stream) drawn preferably in the vicinity of thebottom, and the cyclohexanone effluent drawn at a location in betweenthe two, preferably higher than the location where stream 413 is fedinto the distillation column.

Example 5

FIG. 5 schematically illustrates a process/system 501 operating toproduce cyclohexanone from a first feed mixture comprisingcyclohexylbenzene, phenol, cyclohexanone, water, light acids,2-cyclohexenone, and 3-cyclohexenone. The first feed mixture stream 503is fed into a first distillation column 505 at a first feed mixturefeeding location, where a lower effluent stream 507 preferably in thevicinity of the bottom of column 505 comprising cyclohexylbenzene,bicyclohexane, and other optional heavy components is produced. Stream507 can be further separated to obtain a substantially pure stream ofcyclohexylbenzene and then recycled to an upstream oxidation reactor(not shown) where cyclohexylbenzene is oxidized to formcyclohexylbenzene hydroperoxide. From column 505, a middle effluent 509is drawn at a middle effluent location above the first feed mixturelocation, but below the top of column 505. Stream 509, comprisingcyclohexanone, phenol, cyclohexanol, 3-cyclohexenone, optionallycyclohexylbenzene, optionally bicyclohexane, and optionally2-cyclohexenone, is then fed into a hydrogenation reactor 513 togetherwith a stream of hydrogen 511. In the presence of a bed of hydrogenationcatalyst installed inside reactor 513, 2-cyclohexenone, 3-cyclohexenone,and phenol undergo hydrogenation reactions to form cyclohexanone,cyclohexanone undergoes hydrogenation to form cyclohexanol, and theoptional cyclohexylbenzene, if present, undergoes hydrogenation to formbicyclohexane. Hydrogenation of 2-cyclohexenone and 3-cyclohexenone arebelieved to be much faster than phenol hydrogenation under typicalphenol hydrogenation conditions in the presence of the phenolhydrogenation catalyst. As such, the hydrogenation reactor effluent 515comprises cyclohexanone and cyclohexanol at higher concentrations thanstream 509, phenol at a reduced concentration than stream 509, andoptional cyclohexylbenzene and bicyclohexane, and is depleted in(preferably substantially free) of 2-cyclohexenone and 3-cyclohexenone.Stream 515 is recycled back to the first distillation column 505 at afirst recycle stream location above the first middle effluent location,where it is further separated. Above the first recycle stream location,an upper effluent 517 is produced at a location preferably in thevicinity of the top of column 505. One can also separate stream 515using convention hydro-processing equipment such as high-pressureseparation drum to obtain a hydrogen stream, which can be supplied tothe hydrogenation reactor as a portion of hydrogen stream 511.

Stream 517 comprises cyclohexanone, cyclohexanol, water, and other lightcomponents such as light acids and is substantially free of phenol. Asdemonstrated in Example 1, 3-cyclohexenone cannot be separated fromcyclohexanone using simple, conventional distillation. To reduce theamount of 3-cyclohexenone in stream 517, the present inventors havefound that, by (i) controlling the recycle location to be in the rangefrom 6 to 30, preferably from 10 to 25, more preferably from 10 to 20,still more preferably from 10 to 18, still more preferably 10 to 15,stages above the middle effluent location, and preferably but notnecessarily also (ii) operating the hydrogenation reactor at a phenolconversion no greater than 80% (or no greater than 70%, 60%, 50%, oreven 40%, preferably in the range from 30% to 70%, more preferably inthe range from 35% to 60%, still more preferably in the range from 40%to 50%), and preferably but not necessarily also (iii) controlling theflow rate of stream 509, one can substantially suppress the upwardtravel of 3-cyclohexenone to beyond the recycle location, and channelsubstantially all 3-cyclohexenone into the first middle effluent 509where it is then desirably substantially completely hydrogenated. Ingeneral, a higher flow rate of stream 509 favors the suppression of theupward travel of 3-cyclohexenone. At high phenol conversions higher than80%, flow rate at stream 509 must be substantially increased, reducingthe phenol concentration in the hydrogenation reactor and increasingenergy usage.

Without intending to be bound by a particular theory, it is believedthat such configuration of column 505 and the hydrogenation reactor 513results in substantial quantity of liquid supplied into column 505 viastream 515, a significant portion of which travels downwards to trapsubstantially all of the 3-cyclohexenone in the zone between the middleeffluent location and the recycle location, the preferentialdistribution of 3-cyclohexenone in the middle effluent 509 andsubsequent abatement thereof via hydrogenation in hydrogenation reactor513.

Stream 517, substantially free of phenol and 3-cyclohexenone, is thensupplied to a second distillation column 519, where it is separated toobtain a light component-rich upper stream 521 comprising water, andlight acids, and a cyclohexanone-rich lower effluent stream 523comprising cyclohexanone and cyclohexanol.

Stream 523 is then fed into a third distillation column 525, where it isseparated into a cyclohexanone upper effluent stream 527 and a lowereffluent stream 529. Stream 527 can comprise cyclohexanone at a purityof higher than 99 wt %, preferably higher than 99.5 wt %, morepreferably higher than 99.9 wt %. Stream 529 can comprise cyclohexanolat any concentration depending on the degree of separation in the thirddistillation column, but preferably in the range from 0 to 90 wt %, morepreferably from 10 to 40 wt %. Streams 527 and 529 can be delivered toproduct storage and used for downstream applications such as productionsof caprolactam, adipic acid, and the like. Stream 529, if containingcyclohexanol at substantial quantity, can be either sold and used as aKA oil product, or dehydrogenated to make additional quantity ofhigh-purity cyclohexanone.

In FIG. 5, two distillation columns 519 and 525 are utilized to separatestream 517 obtain light component effluent stream 521, the cyclohexanoneeffluent stream 527 and the lower effluent stream 529 (which can be a KAoil stream). Alternatively, the two columns can be combined into asingle column, with the light component effluent drawn preferably in thevicinity of the top, the KA-oil effluent drawn preferably in thevicinity of the bottom, and the cyclohexanone effluent drawn in themiddle.

Assuming a phenol conversion of 30% in phenol hydrogenation, a steadystate process simulation using Schneider Electric Software SimSci Pro/IIof this configuration was performed. 3-cyclohexenone was assumed toreact at 100% conversion to cyclohexanone across the hydrogenationreactor. Ten (10) theoretical stages were assumed between stream 509 and515. The feed mixture 503 comprised 25 wt % phenol, 25 wt %cyclohexanone, 42 wt % cyclohexylbenzene, 100 ppm 3-cyclohexenone, and0-8 wt % other impurities. The 3-cylohexenone concentration in feed andproduct streams is given below. As can be seen, concentrations of3-cyclohexenone in both the cyclohexanone product stream (stream 527)and stream 529 are exceedingly low, much lower than its concentration infeed mixture stream 503, indicating substantially complete and highlyeffective abatement of 3-cyclohexenone in the process. This is in starkcontrast to the result in comparative Example 2 above, where the firstrecycle stream location was only 2 stages above the first middleeffluent location. Stream 527, with such low concentration of3-cyclohexenone, can be advantageously used for the production ofhigh-quality caprolactam for use in making nylon-6. Stream 529, with itslow concentration of 3-cyclohexenone, can be advantageously used for theproduction of high-quality adipic acid, and the like, for use in makingnylon-6,6, and the like.

Concentration of 3- Stream cyclohexenone (ppm) Feed Mixture (Stream 503)100.1 Cyclohexanone Product (Stream 527) 0.36 Lower Effluent (Stream529) 0.15

Example 6

A mixture comprising 39 wt % phenol, 56 wt % cyclohexanone, 0.1 wt %cyclohexanol, 3686 ppm by weight of 2-cyclohexenone, and an undeterminedconcentration of 3-cyclohexenone was passed through a hydrogenationreactor with a stream of hydrogen in the presence of a hydrogenationcatalyst operating at a pressure of 34 psi (234 kPa, gauge) and at 150°C. Analyses of the feed and the hydrogenated effluent showed that both2-cyclohexenone and 3-cyclohexenone were substantially all converted andresulted in a concentration of 3-cyclohexenone in the hydrogenatedmixture of no higher than 20 ppm (or even no higher than 10 ppm) byweight, and a total concentration of 2-cyclohexenone and 3-cyclohexenonecombined of no higher than 20 ppm (or even no higher than 10 ppm) byweight, based on the total weight of the hydrogenated effluent.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

The contents of all references cited herein are incorporated byreference in their entirety.

1. A process for producing cyclohexanone from a first feed mixturecomprising cyclohexylbenzene, cyclohexanone, phenol, and3-cyclohexenone, the process comprising: feeding the first feed mixtureinto a first distillation column at a first feeding location on thefirst distillation column; obtaining a cyclohexylbenzene-rich lowereffluent from the first distillation column; obtaining a first uppereffluent from a first upper effluent location on the first distillationcolumn above the first feeding location, the first upper effluentcomprising phenol, cyclohexanone, and 3-cyclohexenone; feeding at leasta portion of the first upper effluent to a hydrogenation reactor, wherethe first upper effluent contacts with hydrogen in the presence of ahydrogenation catalyst under hydrogenation conditions to produce ahydrogenation reactor effluent substantially free of 3-cylcohexenone;feeding at least a portion of the hydrogenation reactor effluent to asecond distillation column, and obtaining an cyclohexanone-rich uppereffluent and a phenol-rich lower effluent from the second distillationcolumn.
 2. The process of claim 1, wherein the concentration of3-cyclohexenone in the first feed mixture is in the range from 30 ppm byweight to 1 wt %, based on the total weight of the first feed mixture.3. The process of claim 1, wherein in the hydrogenation reactor, theconversion of 3-cyclohexenone is at least 95%.
 4. The process of claim1, wherein the first feed mixture further comprises 2-cyclohexenone at aconcentration in the range from 30 ppm by weight to 1 wt %, based on thetotal weight of the first feed mixture, the conversion of2-cyclohexenone in the hydrogenation reactor is at least 95%, and thehydrogenation reactor effluent is substantially free of 2-cyclohexenone.5. The process of claim 1, wherein in the hydrogenation reactor, theconversion of phenol is in the range from 30% to 99%.
 6. The process ofclaim 1, further comprising feeding at least a portion of thephenol-rich lower effluent to the first distillation column at a secondfeeding location.
 7. The process of claim 6, wherein the second feedinglocation is higher than the first feeding location and lower than thefirst upper effluent location.
 8. The process of claim 6, wherein atleast a portion of the phenol-rich lower effluent is recycled to thehydrogenation reactor.
 9. The process of claim 1, further comprising:injecting a first stream of hydrogen into the second distillation columnat a location in the vicinity of the bottom of the second distillationcolumn; separating at least a portion of the hydrogen from thecyclohexanone-rich upper effluent from the second distillation column toobtain a second stream of hydrogen; and feeding at least a portion ofthe second stream of hydrogen into the hydrogenation reactor.
 10. Theprocess of claim 1, wherein the first feed mixture further compriseswater and light acids, the first upper effluent comprises water andlight acids, and the first upper effluent is stripped of water and/orlight acids before being fed into the hydrogenation reactor.
 11. Theprocess of claim 1, wherein the first feed mixture comprises water andlight acids, and the process further comprises obtaining a second uppereffluent from the first distillation column at a second upper effluentlocation on the first distillation column above the first upper effluentlocation, wherein the second upper effluent comprises water and lightacids, and is substantially free of phenol.
 12. The process of claim 1,further comprising: feeding at least a portion of the cyclohexanone-richupper effluent from the second distillation column into a thirddistillation column; obtaining a light-components-rich upper effluentfrom the third distillation column; obtaining alight-components-depleted lower effluent from the third distillationcolumn; feeding at least a portion of the light-components-depletedeffluent into a fourth distillation column; and obtaining acyclohexanone upper effluent and a lower effluent from the fourthdistillation column.
 13. The process of claim 12, wherein thecyclohexanone upper effluent from the fourth distillation columncomprises 3-cyclohexenone and/or 2-cyclohexenone each at a concentrationno greater than 20 ppm by weight, based on the total weight of thecyclohexanone effluent.
 14. The process of claim 1, wherein the firstfeed mixture comprises cyclohexylbenzene at a concentration in the rangefrom 20 to 70 wt %, cyclohexanone at a concentration in the range from10 to 40 wt %, phenol at a concentration in the range from 10 to 40 wt%, and 3-cyclohexenone at a concentration in the range from 30 ppm byweight to 1 wt %, based on the total weight of the first feed mixture.15. The process of claim 1, wherein the hydrogenation catalyst comprisesone or more of the following elements: Fe, Co, Ni, Ru, Rh, Pd, Re, Os,Ir, and Pt, and the hydrogenation conditions comprise a temperature inthe range from 25 to 300° C. and a hydrogen partial pressure in therange from 50 to 2000 kPa.
 16. The process of claim 1, wherein the firstfeed mixture is produced by a process comprising: contacting benzenewith hydrogen in a hydroalkylation reactor under hydrogenationconditions to produce a hydroalkylation effluent comprisingcyclohexylbenzene; oxidizing at least a portion of the cyclohexylbenzeneto obtain an oxidized stream comprising cyclohexylbenzene hydroperoxideand cyclohexylbenzene; contacting at least a portion of the oxidizedstream with an acid in a cleavage reactor to obtain a cleavage effluentcomprising phenol, cyclohexanone, and 3-cyclohexenone; and obtaining thefeed mixture from the cleavage mixture.
 17. A process for producingcyclohexanone from a first feed mixture comprising cyclohexylbenzene,cyclohexanone, phenol, and 3-cyclohexenone, the process comprising:feeding the first feed mixture into a first distillation column at afirst feeding location; providing a reactive hydrogenation zone loadedwith a hydrogenation catalyst in the first distillation column above thefirst feeding location; supplying hydrogen into the first distillationcolumn at a location lower than the hydrogenation zone; converting atleast a portion of the 3-cyclohexenone in the hydrogenation zone underhydrogenation conditions; obtaining a cyclohexylbenzene-rich lowereffluent from the first distillation column; and obtaining a first uppereffluent from a first upper effluent location on the first distillationcolumn above the reactive hydrogenation zone, the first upper effluentcomprising cyclohexanone and is substantially free of 3-cyclohexenoneand phenol.
 18. The process of claim 17, wherein in the concentration of3-cyclohexenone in the first feed mixture is in the range from 30 ppm byweight to 1 wt %, based on the total weight of the first feed mixture,and in the hydrogenation zone, the conversion of 3-cyclophexenone is atleast 95%.
 19. The process of claim 17, wherein the first feed mixturefurther comprises 2-cyclohexenone at a concentration in the range from30 ppm by weight to 1 wt %, based on the total weight of the first feedmixture, the conversion of 2-cyclohexenone in the hydrogenation zone isat least 95%, and the first upper effluent is substantially free of2-cyclohexenone.
 20. The process of claim 17, wherein the first feedmixture comprises water and light acids, and the process furthercomprises obtaining a second upper effluent from the first distillationcolumn at a second upper effluent location above the first uppereffluent location, wherein the second upper effluent comprises water andlight acids.
 21. The process of claim 17, further comprising: feeding atleast a portion of the first upper effluent into a second distillationcolumn; obtaining a light-components-rich upper effluent from the seconddistillation column; obtaining a light-components-depleted lowereffluent from the third distillation column; feeding at least a portionof the light-components-depleted lower effluent into a fourthdistillation column; and obtaining an cyclohexanone upper effluent and alower effluent from the fourth distillation column.
 22. The process ofclaim 21, wherein the cyclohexanone upper effluent comprises2-cyclohexenone and/or 3-cyclohexenone each at a concentration nogreater than 10 ppm by weight, based on the total weight of thecyclohexanone upper effluent.
 23. The process of claim 17, wherein thefirst feed mixture comprises cyclohexylbenzene at a concentration in therange from 20 to 70 wt %, cyclohexanone at a concentration in the rangefrom 10 to 40 wt %, phenol in the range from 10 to 40 wt %, and2-cyclohexenone and/or 3-cyclohexenone each at a concentration in therange from 30 ppm by weight to 1 wt %, based on the total weight of thefirst feed mixture.
 24. The process of claim 17, wherein thehydrogenation catalyst comprises one or more of the following elements:Fe, Co, Ni, Ru, Rh, Pd, Re, Os, Ir, and Pt, and the hydrogenationconditions comprise a temperature in the range from 25 to 300° C. and ahydrogen partial pressure in the range from 50 to 2000 kPa.
 25. Theprocess of claim 17, wherein the first feed mixture is produced by aprocess comprising: contacting benzene with hydrogen in ahydroalkylation reactor under hydroalkylation conditions to produce ahydroalkylation effluent comprising cyclohexylbenzene; oxidizing atleast a portion of the cyclohexylbenzene to obtain an oxidized streamcomprising cyclohexylbenzene peroxide and cyclohexylbenzene; contactingat least a portion of the oxidized stream with an acid in a cleavagereactor to obtain a cleavage effluent comprising phenol, cyclohexanone,and 3-cyclohexenone; and obtaining the feed mixture from the cleavagemixture.